Re: v2.35.0 DEVELOPER=1 regression (was: [PATCH] config.mak.dev: specify -std=gnu99 for gcc/clang)

> [I'm aware that Jeff probably won't read this in his sabbatical, just
> replying to the relevant thread]
> 
> Something neither of us considered at the time, but which is pretty
> obvious in retrospect, is that this new -std=gnu99 dosen't only apply to
> our own code, but any system and library includes that we need.
> 
> Thus e.g. FreeBSD 13.0 which previously was happy to compile under
> DEVELOPER=1 will now die because its core libraries use C11-specific
> code:
>     
>     archive.c:337:35: error: '_Generic' is a C11 extension [-Werror,-Wc11-extensions]
>                     strbuf_addstr(&path_in_archive, basename(path));
>                                                     ^
>     /usr/include/libgen.h:61:21: note: expanded from macro 'basename'
>     #define basename(x)     __generic(x, const char *, __old_basename, basename)(x)
>                             ^
>     /usr/include/sys/cdefs.h:325:2: note: expanded from macro '__generic'
>             _Generic(expr, t: yes, default: no)
>             ^