Fix eval.t under minitest, inadvertently broken by 0d804ff61f3a2df2

Fix eval.t under minitest, inadvertently broken by 0d804ff61f3a2df2

That change attempted to skip if use Devel::Peek failed with a skip message of
of $@. Unfortunately, in this situation, $@ has multiple lines, which is not
valid as a skip message. So instead skip if we're miniperl, or we haven't built
Devel::Peek, otherwise attempt to run the test.