Makefile.inc: Explicitly set GNU11 as C language standard

Different compiler versions use a different C language standard by
default.

GCC 4.9 uses GNU89 by default [1], while GCC 5.x uses GNU11 [2].

The discussion on the mailing list in thread *[RFC] Setting C99 by
default* [3] resulted in the preference of C11, which results in build
errors.

So explicitly set it to GNU11, which is also what the current coreboot
toolchain with GCC 5.3 is using.

[1] https://gcc.gnu.org/onlinedocs/gcc-4.9.4/gcc/C-Dialect-Options.html
[2] https://gcc.gnu.org/onlinedocs/gcc-5.4.0/gcc/Standards.html
[3] https://www.coreboot.org/pipermail/coreboot/2016-November/082541.html

Change-Id: If1569618f8044925ff72dcf3543480b34d4f90d6
Signed-off-by: Paul Menzel <pmenzel@molgen.mpg.de>
Reviewed-on: https://review.coreboot.org/17636
Reviewed-by: Julius Werner <jwerner@chromium.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Tested-by: build bot (Jenkins)
Tested-by: Raptor Engineering Automated Test Stand <noreply@raptorengineeringinc.com>

0 files changed, 0 insertions, 0 deletions