Hmm. We changed the '-Wl,$lib' specifically for MSYS, because we need
the shell to do the path conversion to w32 paths here. We could use
'-Xlinker --enable-auto-image-base' as well, I guess, for consistency,
but then again all linker flags passed by the user will have '-Wl,'
prefixed, so that would still be inconsistent. OTOH, changing all to
'-Xlinker' uses a tiny bit more command line length, a scarce resource
on w32. We could also separate mingw from cygwin setting here..
Shrug. I don't know. What do you like best?