We may not emit some inlining remarks under -O0 (which seems
reasonable), so use -O1 in these tests.
This happens to make it pass when the legacy PM is turned on by default.
Previously some RUN lines were failing due to differences in the two
pass managers.
For now we have to use -mllvm -mandatory-inlining-first=false, or else
always_inline inlines don't have remarks emitted due to implementation
details.