[Mesa-dev] [PATCH] m4: Use older autoconf 2.63 compatible ax_check_compile_flag.

[Matt Turner]

Reviewed-by: Matt Turner <mattst88 at gmail.com>

I checked the revision history of this, and it changed between #serial
3 and 4 with a commit message saying it was "Modernizing" it [1]. Not
compelling enough.

[1] http://git.savannah.gnu.org/gitweb/?p=autoconf-archive.git;a=commit;h=1a869696e4129279f7b99c3f9052717354b79a86