Fix Mac builds when using llvm.

supports_llvm needs to include is_mac.

Bug chromium:966543

Change-Id: Ieedf1bba3948de8c75d8bd07473fa2cb0a1e4299
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/32032
Reviewed-by: Alexis Hétu <sugoi@google.com>
Presubmit-Ready: Sean Risser <srisser@google.com>
Tested-by: Sean Risser <srisser@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
diff --git a/src/Reactor/BUILD.gn b/src/Reactor/BUILD.gn
index b649e4c..ddb2ee1 100644
--- a/src/Reactor/BUILD.gn
+++ b/src/Reactor/BUILD.gn
@@ -18,7 +18,7 @@
   # Subzero produces smaller binaries, but doesn't support ARM64 and MIPS64.
   use_swiftshader_with_subzero =
       target_cpu != "arm64" && target_cpu != "mips64el"
-  supports_llvm = is_linux || is_fuchsia || is_win || is_android
+  supports_llvm = is_linux || is_fuchsia || is_win || is_android || is_mac
 }
 
 config("swiftshader_reactor_private_config") {