bug#57380: 29.0.50; configure --config-cache --with-native-compilation failing

[Eli Zaretskii]

> From: Gerd Möllmann <gerd.moellmann@gmail.com>
> Cc: 57380@debbugs.gnu.org
> Date: Wed, 24 Aug 2022 15:37:16 +0200
> 
> Gerd Möllmann <gerd.moellmann@gmail.com> writes:
> 
> >
> > Gerd Möllmann <gerd.moellmann@gmail.com> writes:
> >
> >> AC_RUN_IFELSE is apparently run differently when using the cache, or
> >> something like that.
> >
> > Success and failure
> >
> > configure:19674: gcc -o conftest -g3 -O2 ...   conftest.c
> > configure:19674: gcc -o conftest -g -O2  ...   conftest.m
> >                                                        ^^
> >
> > Baffled.
> 
> diff --git a/configure.ac b/configure.ac
> index 7616e450d0..08a41a7808 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -4273,6 +4273,7 @@ AC_DEFUN
>        [], [libgccjit_not_found])
>      AC_CHECK_HEADERS([libgccjit.h], [], [libgccjit_dev_not_found])
>      # Check if libgccjit really works.
> +    AC_LANG(C)
>      AC_RUN_IFELSE([libgccjit_smoke_test], [], [libgccjit_broken])
>      HAVE_NATIVE_COMP=yes
>      case "${opsys}" in
> 
> This makes it work for me.

Doh!  Do you understand why it is only needed in one of the two cases?

And doesn't it affect the following tests?

> It that something for emacs-28, or rather not? Guess not, but just in
> case.

What does this call produce in the configure script?