getopt-gnu: suppress core dumps from detection code

* m4/getopt.m4 (gl_GETOPT_CHECK_HEADERS): Use the nocrash module
to suppress core dumps that may well occur on glibc systems.
These core dumps might not be cleaned up automatically, or could
trigger some system core dump handling logic.
* modules/getopt-gnu: Depend on nocrash.

Signed-off-by: Pádraig Brady <P@draigBrady.com>