Suppress bad-function-cast warning

Bug: skia:
Change-Id: Ic5efe371b6365913a47d833c698958cc842d16ae
Reviewed-on: https://skia-review.googlesource.com/128685
Commit-Queue: Brian Osman <brianosman@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>
Auto-Submit: Brian Osman <brianosman@google.com>
Reviewed-by: Mike Klein <mtklein@chromium.org>
diff --git a/gn/BUILD.gn b/gn/BUILD.gn
index ac036c2..7a6a821 100644
--- a/gn/BUILD.gn
+++ b/gn/BUILD.gn
@@ -385,6 +385,7 @@
 
     # We are unlikely to want to fix these.
     cflags += [
+      "-Wno-bad-function-cast",
       "-Wno-covered-switch-default",
       "-Wno-deprecated",
       "-Wno-missing-noreturn",