stop disabling threadsafe statics

Chrome's got threadsafe statics, Android too, Flutter too, and heck, we even have them on all our Windows builds.  No one responded to my mail about them.  Let's stop turning them off on not-Windows!

Change-Id: Iadf00336aa73df3f694ac019c9d54a3f2257a3bd
Reviewed-on: https://skia-review.googlesource.com/11683
Reviewed-by: Ben Wagner <bungeman@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>
1 file changed