This is something I hadn't previously done, but there are
cases where it's needed, e.g., building 'wlantest' and then
one of the tests/fuzzing/*/ projects, they use a different
configuration (fuzzing vs. not fuzzing).
Perhaps more importantly, this gets rid of the last thing
that was dumped into the source directories, apart from
the binaries themselves.
Note that due to the use of thin archives, this required
building with absolute paths.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
