[PATCH] ci: Check for necessary Debian packages when running build-many-glibcs.py

[Florian Weimer]

* Lukasz Majewski:

> The build-many-glibc.py can be run on a 'vanila' Debian distribution
> (as for example in docker container), which don't have by default
> installed some packages (like flex).
>
> This causes build break at late stage of the full build;
> ../src/scripts/build-many-glibcs.py . checkout --replace-sources &&
> ../src/scripts/build-many-glibcs.py . host-libraries &&
> ../src/scripts/build-many-glibcs.py . compilers &&
> ../src/scripts/build-many-glibcs.py . glibcs
>
> To avoid such situation, this check has been added to inform user
> early of required (and missing) Debian packages.
>
> The same approach (with using the 'distro' python module) can be
> applied to Fedora or Suse.

I would recommend searching for required tools on PATH, using
shutil.which.  This should work on any distribution.  If I recall
correctly, the non-obvious tools are:

bison
flex
git
makeinfo
patch
tar

Thanks,
Florian