[Configure patch] Issue error if bison not found

[Hans-Peter Nilsson]

On Thu, 28 Nov 2002, Craig Rodrigues wrote:
> Without the following patch, if you try to configure
> on a system which does not have bison installed,
>  ${build_dir}/gcc/Makefile will be generated with the following line:
>
> BISON=false
>
> This causes weird errors later on during a bootstrap, because
> something like:
>
> $(srcdir)/c-parse.c: $(srcdir)/c-parse.y
>         cd $(srcdir) && \
>         if $(BISON) $(BISONFLAGS) -o c-p$$$$.c c-parse.y; then \
>           test -f c-p$$$$.output && mv -f c-p$$$$.output c-parse.output ; \
>           mv -f c-p$$$$.c c-parse.c ; \
>         else \
>           rm -f c-p$$$$.* ; \
>           false ; \
>         fi
>
>
> will be executed as:
>
>         if false -o -c........; then

But shouldn't happen on official released code.

Anyway, this is what the script "missing" in the toplevel dir is
for IIUC.

brgds, H-P