use fcntl() to lock/unlock fds

This is portable back to older Android NDK APIs.
Seems to work fine.

Change-Id: I1f121f372d376909011ffd7063b73cbe50402a5f
Reviewed-on: https://skia-review.googlesource.com/40688
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>
1 file changed