coverage: pass .lcovrc config file to genhtml

The .lcovrc file can contain several directives for genhtml, mostly
pertaining the visualisation of the generated HTML report. Passing the
config file to genhtml allows the user to customize their report.

Fixes #12863

mesonbuild/scripts/coverage.py

@@ -145,7 +145,7 @@ def coverage(outputs: T.List[str], source_root: str, subproject_root: str, build
                                    '--legend',
                                    '--show-details',
                                    '--branch-coverage',
-                                   covinfo])
+                                   covinfo] + lcov_config)
             outfiles.append(('Html', pathlib.Path(htmloutdir, 'index.html')))
         elif gcovr_exe and mesonlib.version_compare(gcovr_version, '>=3.3'):
             htmloutdir = os.path.join(log_dir, 'coveragereport')