package/archlinux: adapt to lcov 2.0 changes.

package/archlinux/PKGBUILD-coverage

@@ -94,7 +94,8 @@ check() {
     rm -rf coverage
     mkdir coverage
     # Keep in sync with package/ci/appveyor-lcov.sh and 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/Magnum*/*" --output-file coverage.info > /dev/null
     lcov --remove coverage.info "*/src/MagnumExternal/*" --output-file coverage.info > /dev/null
     lcov --remove coverage.info "*/Test/*" --output-file coverage.info > /dev/null