clang-tidy9.0.0 added a new check: bugprone-branch-clone
(https://releases.llvm.org/9.0.0/tools/clang/tools/extra/docs/ReleaseNotes.html)
This doesn't like both branches of an if are the same.
This lead to a warning in rainbow, as where the maximum of two values (which
are always the same) is computed in a macro.
I don't always agree with this warning, but here I think it's worth to
remove the macro.
* Enable valgrind exit errorcode
It seems we were not doing anything with the valgrind results... D:
* Use --exit-on-first-error if available
* Revert "Merge pull request #182 from PQClean/rainbow"
This reverts commit 8a008417fe, reversing
changes made to d4b612fe9a.
