sanity: Further improve directory sanity tests

Add tests to ensure COREBASE/TMPDIR doon't contain ".." as this causes
hard to understand build failures.

Also rework the code to test TMPDIR and COREBASE for all the patterns
since they may be set differently and one may contain problematic
characters.

[YOCTO #14111]

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