Configurations/unit-Makefile.tmpl: Don't clean away dotted files

A local 'make clean' did some sweeping removals of files execpt for
the .git directory.  This is a little too sweeping, as other dotted
files might be cleaned away if they happen to match the pattern that's
searched for.

An example is a symlink .dir-locals.el that would keep disappearing if
you build in the source tree and do a make clean...

So we change this to leave all dotted files alone.  Our builds do not
produce such files anyway, so this is a harmless (or rather, less
harmful) change.

Reviewed-by: Paul Dale <paul.dale@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/9573)

(cherry picked from commit 853094dbe15a49b334f3488fc99a557abf021c09)