gn format gn/BUILD.gn

It wants a blank line before a comment, even though the comment isn't a
break.

Change-Id: I6a2988719942e5e72142b8484182c128392a4be8
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/279842
Commit-Queue: Ben Wagner <bungeman@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
Auto-Submit: Ben Wagner <bungeman@google.com>
1 file changed