It just can't be that simple, can it? Well, for *libgcc* I guess it can,
because there is no libgcc.la. However, we also need similar
functionality for the other runtime libraries, but they DO have .la
files which throws a monkey wrench into the mix.
Oh, I just thought of something. The user would need to ensure that
when libtool is generated (e.g. during configure), LDFLAGS includes the
intended -{shared,static}-libgcc flag. Otherwise, libtool's *_postdeps
variable will not include the "correct" list of libraries. But then,
what happens if you use a different -{static,shared}-libgcc at actual
linktime? Or if you link some targets one way, and other targets the
other way?