Hello,

Preparing a set of changes to support shared libs for VxWorks (again),
this patch makes sure that shared libraries for this family of targets
are only built on explicit request, when configured with --enable-shared
(by passing down --disable-shared to subdirs otherwise).

This provides us with a robust way to guard the relevant pieces in
other configure scripts and reduces the risks of accidentally breaking
a platform not yet ready for it, should enable-shared be implicitly
set without this change.

We have been using this for a while now in gcc-11 based production
toolchains with and without shared lib support (depending on the CPU).

I have performed a couple of build + test checks with gcc-12 for
powerpc64, then bootstrapped and regression tested on x86_64-linux.

Committing to mainline shortly.

Best Regards,

Olivier

2022-09-29  Olivier Hainque  <hainque@adacore.com>

        * configure.ac (*vxworks*): If enable_shared is not
        set, set to "no" and add --disable-shared to target and
        host_configargs.
        * configure: Regenerate.