Stop listing `.gcno` files as outputs when using LLVM coverage map format #22132

…rmat When using `--experimental_use_llvm_covmap`, no `.gcno` files are output. By listing them as outputs there is a mismatch between expected and actual outputs. Bazel will create these empty files after the action is run, but they non-deterministically get counted in the Action outputs, which can lead to cache misses on subsequent runs. Signed-off-by: Brentley Jones <github@brentleyjones.com>