[utils][UpdateTestChecks] Warn about possible target triple mismatch (#149645)

Aims to improve error reporting by printing a warning if the target
function regex that has been selected finds no matches. For example, a
`-mtriple=arm64-apple-darwin` runline, would map to the `arm64` prefix
by `update_llc_test_checks.py` and wouldn't match Apple's function
layout, generating some not understandable garbage checks.

The implementation changes `common.process_run_line` to return an
abstract indicator of number of functions processed, without breaking
the drivers. Then `update_llc_test_checks.py` prints a driver specific
error message.

0 files changed, 0 insertions, 0 deletions