gh-157899: Define HAVE_FREADLINK_RUNTIME on FreeBSD 16 (GH-159397)

The commit 4b0e334843b76043c8e69b16ceb4c8478f134c01 added support for
freadlink() on macOS. The function is also available on FreeBSD 16.
Define HAVE_FREADLINK_RUNTIME on FreeBSD.
1 file changed