chrpath: properly handle rootdir with '..' in path

When there is a '..' in the rootdir path, rootdir will not be a substring of
fpath.  This causes an incorrect rpath of the difference between the workdir
and the sysroot to be computed, which is incorrect.  Normalizing basedir
fixes this issue.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>