Buildroot side of change to narrow Windows Android arm hack (#645)

Author: zanderso

build/config/BUILDCONFIG.gn

@@ -531,7 +531,11 @@ if (custom_toolchain != "") {
   } else if (host_os == "mac") {
     host_toolchain = "//build/toolchain/mac:clang_$host_cpu"
   } else if (host_os == "win") {
-    host_toolchain = "//build/toolchain/win:$current_cpu"
+    if (is_clang) {
+      host_toolchain = "//build/toolchain/win:clang_$host_cpu"
+    } else {
+      host_toolchain = "//build/toolchain/win:$host_cpu"
+    }
   } else {
     assert(false, "Unknown host for android cross compile")
   }

build/toolchain/win/BUILD.gn

@@ -61,7 +61,7 @@ if (current_toolchain == default_toolchain) {
                 "copy_dlls",
                 rebase_path(root_build_dir),
                 configuration,
-                target_cpu,
+                current_cpu,
               ])
 }
 
@@ -284,6 +284,13 @@ if (target_cpu == "x64") {
   }
 }
 
+if (target_cpu == "arm") {
+  # When the target cpu is "arm", we use the 32-bit intel toolchain "x86".
+  win_toolchains("x86") {
+    toolchain_arch = "x86"
+  }
+}
+
 if (target_cpu == "arm64") {
   win_toolchains("arm64") {
     toolchain_arch = "arm64"