package/archlinux: adapt to lcov 2.0 changes.

package/archlinux/PKGBUILD-coverage

@@ -50,7 +50,8 @@ check() {
     rm -rf coverage
     mkdir coverage
     # Keep in sync with package/ci/circleci.yml, please
-    lcov --directory . --capture --output-file coverage.info
+    # TODO figure out a way to avoid adding --ignore-errors mismatch
+    lcov --ignore-errors mismatch --directory . --capture --output-file coverage.info
     lcov --extract coverage.info "*/src/python/*" "*/src/Corrade/*" "*/src/Magnum/*" --output-file coverage.info
     genhtml --output-directory ./coverage coverage.info
 }