Cache the results of checking compiler flag support in XORG_TESTSET_CFLAG

Since checking all those warning flags takes an amount of time I find irritating,
here is an attempt at caching the results of checking compiler warning flag support

A couple of aspects which need definitely need review or testing:

* I've tried to get things right when not the first flag in the list of alternates is
supported, but this really needs testing with a compiler other than gcc

* The cache variable naming policy is a bit opaque me, so the names used may need corecting

* I've tried to be careful, but who knows what portability sins I have committed :-)

This change reduces the time to run the ./configure script produced from a configure.ac
containing just

AC_INIT([test], 1.0)
XORG_COMPILER_FLAGS
XORG_CWARNFLAGS
XORG_STRICT_OPTION
AC_OUTPUT()

from ~60s to ~20s on my cygwin machine, and from ~15s to ~9s on a linux VM running on the
same hardware

v2: AS_TR_SH transforms characters which are invalid in shell variable names, so we don't
have to use sed to transform spaces ourself

Signed-off-by: Jon TURNEY <jon.turney@dronecode.org.uk>
Reviewed-by: Gaetan Nadon <memsize@videotron.ca>

0 files changed, 0 insertions, 0 deletions