build: Support non-standard ldso in executables

src/build/config/gcc/BUILD.gn

@@ -108,6 +108,11 @@ config("executable_config") {
       "-Wl,--disable-new-dtags",
     ]
   }
+
+  # Needed for non-standard ldso on OpenWRT
+  if (current_toolchain == default_toolchain && ldso_path != "") {
+    ldflags += [ "-Wl,--dynamic-linker=${ldso_path}" ]
+  }
 }
 
 # Settings for shared libraries.