[Bug algol68/123733] Bootstrap fails: implicit declaration of GC_is_init_called

[jemarch at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123733

--- Comment #2 from Jose E. Marchesi <jemarch at gcc dot gnu.org> ---
The regression is due to a change in configure.ac that enables the
algol68-gc if libgc is available.

I think the way to go is:

1. To document the minimum version of libgc that is known to work, and
2. To add a configure check to make sure GC_is_init_called is
available.