Import of code from autoconf-archive
This commit updates the code imported from autoconf-archive to
24358c8c5ca679949ef522964d94e4d1cd1f941a (v2019.01.06)
New files are:
m4/ax_append_compile_flags.m4
m4/ax_append_flag.m4
m4/ax_check_compile_flag.m4
m4/ax_gcc_func_attribute.m4
m4/ax_require_defined.m4
Change-Id: I64e14d1b4d41ebfee82fa92da10239f73e28b4c9
Reviewed-on: https://gerrit.openafs.org/14138
Reviewed-by: Cheyenne Wills <cwills@sinenomine.net>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>