[test-suite] Register result codes with lit.

lit currently only has a hard-coded set of result codes and crashes
when encountering test-suite's NOEXE result code. D78164 adds the
possibility to register custom result codes.

This patch registers the result code NOEXE and renames SKIPPED to
NOCHANGE since lit already has a SKIPPED result code.

While this does not fix any buildbot (such as
http://lab.llvm.org:8011/builders/clang-native-arm-lnt-perf), it at
least should allow lit to display which tests have failed at the end.

Reviewed By: yln, jdoerfert

Differential Revision: https://reviews.llvm.org/D79064
4 files changed