Allow using goma on Windows with symbol_level == 2

build/config/compiler/compiler.gni

Index: build/config/compiler/compiler.gni
diff --git a/build/config/compiler/compiler.gni b/build/config/compiler/compiler.gni
index e9e809a9061bceffc3b7b67a3e1697f6d45f5d78..e5087c7816584b57e874cdb553d4068af0836281 100644
--- a/build/config/compiler/compiler.gni
+++ b/build/config/compiler/compiler.gni
@@ -111,6 +111,9 @@ if (symbol_level == -1) {
   } else {
     symbol_level = 0
   }
+} else if (symbol_level == 2) {
+  assert(is_win_fastlink || !use_goma,
+         "Goma builds that use symbol_level 2 must use is_win_fastlink.")
 }
 
 # Assert that the configuration isn't going to hit https://crbug.com/648948.