[libpng] Fix build for qemu

* Fix BUILD file when compiling for qemu

Fixed: 87754
Change-Id: I441e04cc5b3b5a72802adcb97af5ce9e8edb2f8a
Reviewed-on: https://fuchsia-review.googlesource.com/c/third_party/libpng/+/615522
Reviewed-by: David Reveman <reveman@google.com>
1 file changed