FindPython: Enable C language in tests that find the Development component

Since commit 5537ccd8 (FindPython: Tests optimizations, 2020-10-01)
some FindPython tests fail because the Development component cannot be
found without knowing `CMAKE_LIBRARY_ARCHITECTURE`.  Enable at least one
language in each of these test cases to get that value.  This is
consistent with use in practice because the Development component does
not make much sense without a language to compile sources anyway.

Fixes: #21277