Add option to skip emsdk sync

This may be causing oss-fuzz to fail. It's not needed for it anyway.

Change-Id: I30396b6ff6d7ae3f85daebd1f492ff71dd0b3ec2
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/779916
Reviewed-by: Ben Wagner <bungeman@google.com>
1 file changed