Do not use /Brepro for cl.exe with goma

Current goma backend does not support cl.exe execution with /Brepro.

Change-Id: Ie892880488e3ed22b9253bd8f3bc21306f9b0524
Reviewed-on: https://chromium-review.googlesource.com/1016446Reviewed-by: Nico Weber <thakis@chromium.org>
Commit-Queue: Takuto Ikuta <tikuta@chromium.org>
Cr-Commit-Position: refs/heads/master@{#551623}

build/config/win/BUILD.gn

@@ -96,7 +96,7 @@ config("compiler") {
     lib_dirs = [ "$clang_base_path/lib/clang/$clang_version/lib/windows" ]
   }
 
-  if (use_lld && !use_thin_lto) {
+  if (use_lld && !use_thin_lto && (is_clang || !use_goma)) {
     # /Brepro lets the compiler not write the mtime field in the .obj output.
     # link.exe /incremental relies on this field to work correctly, but lld
     # never looks at this timestamp, so it's safe to pass this flag with