* gnu/tests/base.scm (%test-basic-os): Rename to ...
(test-basic-os): ... this, and turn into procedure that takes optional KERNEL
argument.
(%test-basic-os): Use that procedure.
(%test-linux-libre-5.15, %test-linux-libre-5.10, %test-linux-libre-5.4,
%test-linux-libre-4.19, %test-linux-libre-4.14, %test-linux-libre-4.9): New
tests.