configure: use do_cc when checking for -fstack-protector support

MacOSX clang silently swallows unrecognized -f options when doing a link
with '-framework' also on the command line, so to detect support for
the various -fstack-protector options we must do a plain .c to .o compile,
not a complete compile-and-link.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Message-id: 1397041487-28477-1-git-send-email-peter.maydell@linaro.org

configure

@@ -1448,7 +1448,7 @@ done
 if test "$stack_protector" != "no" ; then
   gcc_flags="-fstack-protector-strong -fstack-protector-all"
   for flag in $gcc_flags; do
-    if compile_prog "-Werror $flag" "" ; then
+    if do_cc $QEMU_CFLAGS -Werror $flag -c -o $TMPO $TMPC ; then
       QEMU_CFLAGS="$QEMU_CFLAGS $flag"
       LIBTOOLFLAGS="$LIBTOOLFLAGS -Wc,$flag"
       break