Allow makechrootpkg to install package files in the chroot

This is a very very hackish way to deal with rebuilds for
right now.

The intent is the following:
    First build foobar-1.2
    makechrootpkg -i foobar-1.2-1-i686.pkg.tar.gz
    Now build packages that depend on foobar-1.2

Signed-off-by: Aaron Griffin <aaronmgriffin@gmail.com>