diff --git a/src/build.sh b/src/build.sh
index 94b52a56f2..3c8fbfa1e4 100755
--- a/src/build.sh
+++ b/src/build.sh
@@ -21,6 +21,23 @@ fi
 
 . ./get-sysroot.sh
 
+# ccache
+case "$host_os" in
+  linux|mac)
+    if which ccache >/dev/null 2>&1; then
+      export CCACHE_SLOPPINESS=time_macros
+      export CCACHE_BASEDIR="$PWD"
+      export CCACHE_CPP2=yes
+      CCACHE=ccache
+    fi
+  ;;
+  win)
+    if [ -f "$HOME"/.cargo/bin/sccache* ]; then
+      export PATH="$PATH:$HOME/.cargo/bin"
+      CCACHE=sccache
+    fi
+  ;;
+esac
 if [ "$CCACHE" ]; then
   flags="$flags
     cc_wrapper=\"$CCACHE\""
@@ -59,16 +76,18 @@ if [ "$WITH_SYSROOT" ]; then
     target_sysroot=\"//$WITH_SYSROOT\""
 fi
 
-if [ "$USE_AFDO" ]; then
-  flags="$flags"'
-    clang_sample_profile_path="//chrome/android/profiles/afdo.prof"'
-fi
-
-if [ "$ARCH" = "Darwin" ]; then
+if [ "$host_os" = "mac" ]; then
   flags="$flags"'
     enable_dsyms=false'
 fi
 
+case "$EXTRA_FLAGS" in
+*target_os=\"android\"*)
+  flags="$flags"'
+    is_high_end_android=true'
+  ;;
+esac
+
 if [ "$target_cpu" = "mipsel" -o "$target_cpu" = "mips64el" ]; then
   flags="$flags"'
     use_thin_lto=false
diff --git a/src/get-clang.sh b/src/get-clang.sh
index 3cc2f3fad8..1bb74d3ca9 100755
--- a/src/get-clang.sh
+++ b/src/get-clang.sh
@@ -11,6 +11,21 @@ if [ "$OPENWRT_FLAGS" ]; then
   ./get-openwrt.sh
 fi
 
+# Clang
+# See src/tools/clang/scripts/update.py
+case "$host_os" in
+  linux) WITH_CLANG=Linux_x64;;
+  win) WITH_CLANG=Win;;
+  mac) WITH_CLANG=Mac;;
+esac
+if [ "$host_os" = mac -a "$host_cpu" = arm64 ]; then
+  WITH_CLANG=Mac_arm64
+fi
+mkdir -p third_party/llvm-build/Release+Asserts
+cd tools/clang/scripts
+CLANG_REVISION=$($PYTHON -c 'import update; print(update.PACKAGE_VERSION)')
+cd -
+echo $CLANG_REVISION >third_party/llvm-build/Release+Asserts/cr_build_revision
 if [ ! -d third_party/llvm-build/Release+Asserts/bin ]; then
   mkdir -p third_party/llvm-build/Release+Asserts
   clang_path="clang-$CLANG_REVISION.tgz"
@@ -18,12 +33,59 @@ if [ ! -d third_party/llvm-build/Release+Asserts/bin ]; then
   curl "$clang_url" | tar xzf - -C third_party/llvm-build/Release+Asserts
 fi
 
-if [ "$USE_AFDO" -a ! -f chrome/android/profiles/afdo.prof ]; then
-  afdo_path=$(cat chrome/android/profiles/newest.txt)
-  afdo_url="https://storage.googleapis.com/chromeos-prebuilt/afdo-job/llvm/$afdo_path"
-  curl "$afdo_url" | bzip2 -cd >chrome/android/profiles/afdo.prof
+# sccache
+if [ "$host_os" = win -a ! -f ~/.cargo/bin/sccache.exe ]; then
+  sccache_url="https://github.com/mozilla/sccache/releases/download/0.2.12/sccache-0.2.12-x86_64-pc-windows-msvc.tar.gz"
+  mkdir -p ~/.cargo/bin
+  curl -L "$sccache_url" | tar xzf - --strip=1 -C ~/.cargo/bin
 fi
 
+# GN
+# See src/DEPS
+case "$host_os" in
+  linux) WITH_GN=linux-amd64;;
+  win) WITH_GN=windows-amd64;;
+  mac) WITH_GN=mac-amd64;;
+esac
+if [ "$host_os" = mac -a "$host_cpu" = arm64 ]; then
+  WITH_GN=mac-arm64
+fi
+if [ ! -f gn/out/gn ]; then
+  gn_version=$(grep "'gn_version':" DEPS | cut -d"'" -f4)
+  mkdir -p gn/out
+  curl -L "https://chrome-infra-packages.appspot.com/dl/gn/gn/$WITH_GN/+/$gn_version" -o gn.zip
+  unzip gn.zip -d gn/out
+  rm gn.zip
+fi
+
+# See src/build/config/compiler/pgo/BUILD.gn
+case "$target_os" in
+  win)
+    case "$target_cpu" in
+      arm64) WITH_PGO=win-arm64;;
+      x64) WITH_PGO=win64;;
+      *) WITH_PGO=win32;;
+    esac
+  ;;
+  mac)
+    case "$target_cpu" in
+      arm64) WITH_PGO=mac-arm;;
+      *) WITH_PGO=mac;;
+    esac
+  ;;
+  linux|openwrt)
+    WITH_PGO=linux
+  ;;
+  android)
+    case "$target_cpu" in
+      arm64) WITH_PGO=android-arm64;;
+      *) WITH_PGO=android-arm32;;
+    esac
+  ;;
+esac
+if [ "$WITH_PGO" ]; then
+  PGO_PATH=$(cat chrome/build/$WITH_PGO.pgo.txt)
+fi
 if [ "$WITH_PGO" -a ! -f chrome/build/pgo_profiles/"$PGO_PATH" ]; then
   mkdir -p chrome/build/pgo_profiles
   cd chrome/build/pgo_profiles
@@ -31,21 +93,7 @@ if [ "$WITH_PGO" -a ! -f chrome/build/pgo_profiles/"$PGO_PATH" ]; then
   cd ../../..
 fi
 
-if [ "$USE_SCCACHE" -a ! -f ~/.cargo/bin/sccache.exe ]; then
-  sccache_url="https://github.com/mozilla/sccache/releases/download/0.2.12/sccache-0.2.12-x86_64-pc-windows-msvc.tar.gz"
-  mkdir -p ~/.cargo/bin
-  curl -L "$sccache_url" | tar xzf - --strip=1 -C ~/.cargo/bin
-fi
-
-if [ ! -f gn/out/gn ]; then
-  gn_version=$(grep "'gn_version':" DEPS | cut -d"'" -f4)
-  mkdir -p gn/out
-  curl -L "https://chrome-infra-packages.appspot.com/dl/gn/gn/$WITH_GN-amd64/+/$gn_version" -o gn.zip
-  unzip gn.zip -d gn/out
-  rm gn.zip
-fi
-
-if [ "$USE_ANDROID_NDK" -a ! -d third_party/android_toolchain/ndk ]; then
+if [ "$target_os" = android -a ! -d third_party/android_toolchain/ndk ]; then
   # https://dl.google.com/android/repository/android-ndk-r25c-linux.zip
   android_ndk_version=$(grep 'default_android_ndk_version = ' build/config/android/config.gni | cut -d'"' -f2)
   curl -LO https://dl.google.com/android/repository/android-ndk-$android_ndk_version-linux.zip
@@ -58,6 +106,6 @@ if [ "$USE_ANDROID_NDK" -a ! -d third_party/android_toolchain/ndk ]; then
   cd third_party/android_toolchain/ndk
   find toolchains -type f -regextype egrep \! -regex \
     '.*(lib(atomic|gcc|gcc_real|compiler_rt-extras|android_support|unwind).a|crt.*o|lib(android|c|dl|log|m).so|usr/local.*|usr/include.*)' -delete
-  cd ../..
+  cd -
   rm -rf android-ndk-$android_ndk_version android-ndk-$android_ndk_version-linux.zip
 fi
diff --git a/src/get-sysroot.sh b/src/get-sysroot.sh
index bc3a71b7c4..d220966365 100644
--- a/src/get-sysroot.sh
+++ b/src/get-sysroot.sh
@@ -1,90 +1,58 @@
-ARCH=$(uname)
+eval "$EXTRA_FLAGS"
+
+case "$(uname)" in
+  MINGW*|MSYS*) host_os=win;;
+  Linux) host_os=linux;;
+  Darwin) host_os=mac;;
+  *) echo "Unsupported host OS" >&2; exit 1;;
+esac
+
+case "$(uname -m)" in
+  x86_64|x64) host_cpu=x64;;
+  x86|i386|i686) host_cpu=x86;;
+  arm) host_cpu=arm;;
+  arm64|aarch64|armv8b|armv8l) host_cpu=arm64;;
+  *) echo "Unsupported host CPU" >&2; exit 1;;
+esac
+
+# See src/build/config/BUILDCONFIG.gn
+if [ ! "$target_os" ]; then
+  target_os="$host_os"
+fi
+
+if [ ! "$target_cpu" ]; then
+  target_cpu="$host_cpu"
+fi
 
 PYTHON=$(which python3 2>/dev/null || which python 2>/dev/null)
-mkdir -p third_party/llvm-build/Release+Asserts
-cd tools/clang/scripts
-CLANG_REVISION=$($PYTHON -c 'import update; print(update.PACKAGE_VERSION)')
-cd -
-echo $CLANG_REVISION >third_party/llvm-build/Release+Asserts/cr_build_revision
 
-eval "$EXTRA_FLAGS"
-case "$ARCH" in
-  Linux)
-    if which ccache >/dev/null 2>&1; then
-      export CCACHE_SLOPPINESS=time_macros
-      export CCACHE_BASEDIR="$PWD"
-      export CCACHE_CPP2=yes
-      CCACHE=ccache
-    fi
-    WITH_CLANG=Linux_x64
-    # See build/config/compiler/pgo/BUILD.gn
-    WITH_PGO=linux
-    WITH_GN=linux
-    if [ "$OPENWRT_FLAGS" ]; then
-      eval "$OPENWRT_FLAGS"
-      WITH_SYSROOT="out/sysroot-build/openwrt/$release/$arch"
-    elif [ "$target_os" = android ]; then
-      case "$target_cpu" in
-        arm64) WITH_PGO=android-arm64;;
-        *) WITH_PGO=android-arm32;;
-      esac
-      # Continue to use mac-arm profile while investigating Android results.
-      # TODO(crbug.com/4828524, crbug.com/1308749): Remove the following.
-      WITH_PGO=mac-arm
-      USE_AFDO=
-      USE_ANDROID_NDK=y
-      WITH_SYSROOT=
-      case "$target_cpu" in
-        x64) WITH_ANDROID_IMG=x86_64-24_r08;;
-        x86) WITH_ANDROID_IMG=x86-24_r08;;
-        arm64) WITH_ANDROID_IMG=arm64-v8a-24_r07;;
-        arm) WITH_ANDROID_IMG=armeabi-v7a-24_r07;;
-      esac
-    else
-      case "$target_cpu" in
-        x64) SYSROOT_ARCH=amd64;;
-        x86) SYSROOT_ARCH=i386;;
-        arm64) SYSROOT_ARCH=arm64;;
-        arm) SYSROOT_ARCH=armhf;;
-        mipsel) SYSROOT_ARCH=mipsel;;
-        mips64el) SYSROOT_ARCH=mips64el;;
-        riscv64) SYSROOT_ARCH=riscv64;;
-      esac
-      if [ "$SYSROOT_ARCH" ]; then
-        WITH_SYSROOT="out/sysroot-build/bullseye/bullseye_${SYSROOT_ARCH}_staging"
-      fi
-    fi
-  ;;
-  MINGW*|MSYS*)
-    ARCH=Windows
-    if [ -f "$HOME"/.cargo/bin/sccache* ]; then
-      export PATH="$PATH:$HOME/.cargo/bin"
-      CCACHE=sccache
-    fi
-    WITH_CLANG=Win
-    USE_SCCACHE=y
-    WITH_GN=windows
+# sysroot
+case "$target_os" in
+  linux)
     case "$target_cpu" in
-      arm64) WITH_PGO=win-arm64;;
-      x64) WITH_PGO=win64;;
-      *) WITH_PGO=win32;;
+      x64) SYSROOT_ARCH=amd64;;
+      x86) SYSROOT_ARCH=i386;;
+      arm64) SYSROOT_ARCH=arm64;;
+      arm) SYSROOT_ARCH=armhf;;
+      mipsel) SYSROOT_ARCH=mipsel;;
+      mips64el) SYSROOT_ARCH=mips64el;;
+      riscv64) SYSROOT_ARCH=riscv64;;
     esac
-  ;;
-  Darwin)
-    if which ccache >/dev/null 2>&1; then
-      export CCACHE_SLOPPINESS=time_macros
-      export CCACHE_BASEDIR="$PWD"
-      export CCACHE_CPP2=yes
-      CCACHE=ccache
+    if [ "$SYSROOT_ARCH" ]; then
+      WITH_SYSROOT="out/sysroot-build/bullseye/bullseye_${SYSROOT_ARCH}_staging"
     fi
-    WITH_CLANG=Mac
-    WITH_GN=mac
+  ;;
+  openwrt)
+    eval "$OPENWRT_FLAGS"
+    WITH_SYSROOT="out/sysroot-build/openwrt/$release/$arch"
+  ;;
+  android)
+    WITH_SYSROOT=
     case "$target_cpu" in
-      arm64) WITH_PGO=mac-arm;;
-      *) WITH_PGO=mac;;
+      x64) WITH_ANDROID_IMG=x86_64-24_r08;;
+      x86) WITH_ANDROID_IMG=x86-24_r08;;
+      arm64) WITH_ANDROID_IMG=arm64-v8a-24_r07;;
+      arm) WITH_ANDROID_IMG=armeabi-v7a-24_r07;;
     esac
   ;;
 esac
-if [ "$WITH_PGO" ]; then
-  PGO_PATH=$(cat chrome/build/$WITH_PGO.pgo.txt)
-fi