Remove $CMSIS_BUILD_ROOT references and test structure cleanup #276

All 133 tests pass in 3s

    4 files ±0   36 suites ±0 3s ⏱️ -1s
133 tests ±0 133 ✔️ ±0 0 💤 ±0 0 ❌ ±0
532 runs ±0 532 ✔️ ±0 0 💤 ±0 0 ❌ ±0

Results for commit 242f0d0. ± Comparison against earlier commit 9a3b3d7.