Upstream LLVM fixes #8597, no longer need `-Dskip-debug` and others.

Additionally, due to the nature of drone.io server pool, it is
beneficial to know which aarch64 CPU brand is in use.

- drop `-Dskip-debug` and others
- invoke `lscpu` prior to build
- enable more testsuite consistent with ci azure
- remove workaround for (already closed) #6830

closes #8597