Fix detection of NEON f16 intrinsic availability on GCC

Bug: skia:12061
Bug: skia:14303
Change-Id: I17f855fbf85a21772c3ff650c1411e81d6088aeb
Reviewed-on: https://skia-review.googlesource.com/c/skcms/+/698184
Reviewed-by: John Stiles <johnstiles@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
1 file changed