Force the use of clang-cl.exe for Windows builds.

.cargo/config

@@ -22,5 +22,5 @@ ar = "arm-linux-gnueabihf-ar"
 linker = "aarch64-linux-gnu-gcc"
 ar = "aarch64-linux-gnu-ar"
 
-[target.'cfg(target_os=windows)']
+[target.x86_64-pc-windows-msvc]
-linker = "./support/android/fakeld/fake-ld.cmd"
+linker = "lld-link.exe"

appveyor.yml

@@ -30,6 +30,9 @@ environment:
     C:\\Program Files\\Git\\cmd;\
     C:\\Program Files\\Git\\usr\\bin;\
     C:\\Program Files\\AppVeyor\\BuildAgent;"
+  CC: "clang-cl.exe"
+  CXX: "clang-cl.exe"
+
   matrix:
   - TARGET: nightly-x86_64-pc-windows-msvc
 

components/script/build.rs

@@ -25,11 +25,6 @@ fn main() {
         // We must use Ninja on Windows for this -- msbuild is painfully slow,
         // and ninja is easier to install than make.
         build.generator("Ninja");
-        // because we're using ninja, we need to explicitly set these
-        // to VC++, otherwise it'll try to use cc
-        build
-            .define("CMAKE_C_COMPILER", "cl.exe")
-            .define("CMAKE_CXX_COMPILER", "cl.exe");
         // We have to explicitly specify the full path to link.exe,
         // for reasons that I don't understand.  If we just give
         // link.exe, it tries to use script-*/out/link.exe, which of

python/servo/build_commands.py

@@ -310,6 +310,10 @@ class MachCommands(CommandBase):
         if with_debug_assertions:
             env['RUSTFLAGS'] = env.get('RUSTFLAGS', "") + " -C debug_assertions"
 
+        if sys.platform == "win32":
+            env["CC"] = "clang-cl.exe"
+            env["CXX"] = "clang-cl.exe"
+
         if android:
             if "ANDROID_NDK" not in env:
                 print("Please set the ANDROID_NDK environment variable.")