On asan/win bots building with goma, don't accidentally emit DWARF

build/config/sanitizers/BUILD.gn

Index: build/config/sanitizers/BUILD.gn
diff --git a/build/config/sanitizers/BUILD.gn b/build/config/sanitizers/BUILD.gn
index cf51896225d1dfae31600dc8a573a057b773a17b..3768cb93553872974ffcf685544b21f43525efc9 100644
--- a/build/config/sanitizers/BUILD.gn
+++ b/build/config/sanitizers/BUILD.gn
@@ -231,6 +231,12 @@ config("common_sanitizer_flags") {
   if (using_sanitizer) {
     assert(is_clang, "sanitizers only supported with clang")
     cflags += [ "-gline-tables-only" ]
+    if (is_win) {
+      # Just -gline-tables-only currently causes clang-cl to emit debug info
+      # in DWARF format.
+      # TODO(thakis): Remove this once we have a clang at LLVM r278139+
+      cflags += [ "/Z7" ]
+    }
   }
 
   # Common options for AddressSanitizer, LeakSanitizer, ThreadSanitizer,