Make goma work on win GN builds.

build/config/compiler/BUILD.gn

Index: build/config/compiler/BUILD.gn
diff --git a/build/config/compiler/BUILD.gn b/build/config/compiler/BUILD.gn
index 0d9e501a9be76fd4e19401b69a032bfb1bc61a18..b37da94d6419ec040b61ec8657da763ffb81ad13 100644
--- a/build/config/compiler/BUILD.gn
+++ b/build/config/compiler/BUILD.gn
@@ -951,7 +951,12 @@ config("optimize_max") {
 
 config("symbols") {
   if (is_win) {
-    cflags = [ "/Zi" ]  # Produce PDB file, no edit and continue.
+    import("//build/toolchain/goma.gni")
+    if (use_goma) {
+      cflags = [ "/Z7" ]  # No PDB file
+    } else {
+      cflags = [ "/Zi" ]  # Produce PDB file, no edit and continue.
+    }
     ldflags = [ "/DEBUG" ]
   } else {
     cflags = [ "-g2" ]