* Use a debug build of stage3 instead of a debug build of stage2 for
   our self-hosted compiler test coverage.
 * Move coverage from stage1 to stage3 for:
   - building self-hosted without LLVM
   - building self-hosted for 32-bit arm
   - test-compiler-rt
   - test-behavior
   - test-std
   - test-compare-output
   - test-asm-link
   - test-fmt