* tests/dryrun.test: The constant modifications of libtool would

* tests/dryrun.test: The constant modifications of libtool would
cause main.o to be updated at the wrong time; the new approach is
to modify the libtool script so that it enables dry run depending
on whether an environment variable is set or not.  I've also moved
`after' and `before' to a directory deep within $objdir, instead
of creating it in ../tests.
* tests/Makefile.am (CLEANFILES): Removed.