Add regex-based file exclusion to the clang-tidy runner script.
This allows excluding paths (submodules, vendored code, tests) from
static analysis without modifying .clang-tidy files in each directory.
The -exclude argument accepts a regex pattern that is matched against
file paths from the compilation database. Matching files are skipped.
Example: -exclude="src/lib/foo|src/modules/bar"
This prepares for the clang-tidy v6 to v18 migration where we need
to exclude external code that we consume but don't maintain.
Signed-off-by: Ramon Roche <mrpollo@gmail.com>
