Reproduction case for bazelbuild/bazel#20862

bazel --version
./write.sh a
bazel --ignore_all_rc_files build --experimental_remote_merkle_tree_cache --experimental_remote_merkle_tree_cache_size=0 --disk_cache=~/.cache/bazel_repro_cache //:big

The command takes approximately 2 minutes to complete on bazelbuild/7.0.0, and only a couple of seconds on bazelbuild/6.4.0

Re-run ./write.sh with a new string argument to bust the cache, if desired.