libiberty: install PIC version of libiberty.a
    
    This will install a PIC version of libiberty.a by overwriting the non-PIC
    version of libiberty.a while compiling.  We do this because there is no
    shared version of libiberty for random apps to link against which means if
    someone wants to use this in a shared library or PIE, they're out of luck.
    It's arguable whether people should be able to use this in a shared lib,
    but usage in PIE should be fine.  You could argue that this penalizes the
    non-PIE users, but the counter point is that people using this library in
    general are fairly low, and we'd rather have things work for all of them.