Revert r281055 as it breaks installing test scripts in the mixed PROGS/SCRIPT
case

Repro is as follows:

% sudo pkg install -y kyua
% sudo rm -Rf /usr/tests
% sudo make hier
% (cd lib/libthr/tests/; make obj; make depend; make all; sudo make install)
% (cd /usr/tests/lib/libthr; kyua list)

Failure seen in Jenkins build starting here:
https://jenkins.freebsd.org/job/FreeBSD_HEAD-tests2/927/

Pointyhat to: bapt