Note on --enable-shared

[Tom Tromey]

--enable-shared has the nice feature of letting the user choose what
packages should have shared libraries.  For instance in the gcc tree I
could configure with --enable-shared=libgcc,libgcj to enable just
those shared libraries.

However, it turns out that in this same situation, libgcj really needs
to know whether a shared libgcc is being built.  That's the case
because we're bootstrapping the compiler, and we need to know whether
to specify `-shared-libgcc' when building target executables.

Ordinarily I would do this by looking at $enable_shared in configure.
But it turns out I can't do this because AC_ENABLE_SHARED rewrites
enable_shared.  (And incidentally this means there's no easy way to
build two libraries in a package one shared and one not.  Maybe that's
a non-problem though.)

In my particular situation it turns out there is a workaround.
However, it would be nice if this were changed somehow.

Tom