Allow BROKEN_BUILD to be more specific

Enhance run-tests.sh's BROKEN_BUILD processing
1) if BROKEN_BUILD is an empty file, the test is skipped as before
2) if BROKEN_BUILD exist and non-empty, it contains toolchain versions
   from building the test

Change-Id: I24b3ae61fa1e4714988ec395d13aa78faf9a7f5e
7 files changed