Base clang builds after 2022-07-05 mk: Add support for newer C standards.

[David Shao <davshao%gmail.com@localhost>]

Has someone had an equivalent of a successful bulk build using a
system with base compiler clang after
2022-07-05  mk: Add support for newer C standards.

On both a FreeBSD 12 and a FreeBSD 14 system, I am getting build errors in
x11/xf86-video-nouveau
where a construct such as
typeof(x) __z
is no longer being properly recognized.

Commenting out the recent change in
pkgsrc/mk/compiler/clang.mk

+.for _version_ in ${_C_STD_VERSIONS}
+_C_STD_FLAG.${_version_}?=     -std=${_version_}
+.endfor

allowed xf86-video-nouveau to build successfully.

This reversion may also be fixing a more serious build error in graphics/cairo
on the same FreeBSD 12 and 14 systems.


On the other hand, I am seeing no problems so far with a base gcc
NetBSD amd64 current
system, modular xorg, building through to Firefox.