Description

Unittests don't build in current master.
Quick bisect we did with @miri64 points to #8844 as introducing this problem.

Steps to reproduce the issue

cd tests/unittests
make

or

make tests-<module>

Expected results

It should build.

Actual results

It does not build. Sample error:

make: *** No rule to make target '/home/vagrant/RIOT/tests/unittests/bin/samr21-xpro/tests-tweetnacl.a', needed by '/home/vagrant/RIOT/tests/unittests/bin/samr21-xpro/tests_unittests.elf'.  Stop.

Versions

Issue detected on Linux and OS X