grub2: fix build on gcc where _FORTIFY_SOURCE is defined
* e.g. with gentoo gcc-7.1 they define _FORTIFY_SOURCE by default with:
https://sources.gentoo.org/cgi-bin/viewvc.cgi/gentoo/src/patchsets/gcc/7.1.0/gentoo/10_all_default-fortify-source.patch?view=markup
which results in following error while building grub-efi-native:
./config-util.h:1504:48: error: this use of "defined" may not be portable [-Werror=expansion-to-defined]
|| (defined _FORTIFY_SOURCE && 0 < _FORTIFY_SOURCE \
^~~~~~~~~~~~~~~
this part comes from gnulib and it's used only for Apple and BSD,
so we can ignore it, but we cannot add -Wno-error=expansion-to-defined
because this warning was introduced only in gcc-7 and older gcc
will fail with:
cc1: error: -Werror=expansion-to-defined: no option -Wexpansion-to-defined
use #pragma to work around this
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
