make test more stringent by building separate library
project('modules', 'fortran')
-e = executable('modprog', 'mymod.f90', 'prog.f90', 'comment_mod.f90')
+commented = library('commented', 'comment_mod.f90')
+
+e = executable('modprog', 'mymod.f90', 'prog.f90',
+ link_with: commented)
test('moduletest', e)
