rc_include rc/CC.rc

prog='
#include <time.h>

struct timespec x;
'

x=
rc_replaceln HAVE_POSIX 1
if ! rc_compile cc link "$prog"; then
	x="-D_XOPEN_SOURCE=500"
	rc_appendln CPPFLAGS "$x"
	if ! rc_compile cc link "$prog"; then
		rc_undo
		rc_replaceln HAVE_POSIX ""
	fi
fi
rc_save