A different set of commits, a new test:
...$ git checkout b836deac35cd58c271aebbebdc6b0bd13a058585
...$ rm -rf ~/bazel_cache/
...$ bazel clean --expunge
...$ time bazel build --disk_cache=~/bazel_cache //tensorflow/tools/pip_package:build_pip_package
...
INFO: Elapsed time: 1164.101s, Critical Path: 308.54s
INFO: 11114 processes: 1289 internal, 9825 local.
INFO: Build completed successfully, 11114 total actions

real	19m24.243s
user	0m0.360s
sys	0m0.336s
...$ git checkout b71106370c45bd584ffbdde02be21d35b882d9ee
Previous HEAD position was b836deac35c Remove TensorShape dependency from ScopedMemoryDebugAnnotation.
HEAD is now at b71106370c4 Integrate LLVM at llvm/llvm-project@bd7ece4e063e
...$ time bazel build --disk_cache=~/bazel_cache //tensorflow/tools/pip_package:build_pip_package
...
INFO: Elapsed time: 262.158s, Critical Path: 120.47s
INFO: 1567 processes: 149 internal, 1418 local.
INFO: Build completed successfully, 1567 total actions

real	4m22.240s
user	0m0.095s
sys	0m0.092s

This is around LLVM bump from 23 hours ago, so the two tests run so far cover the bumps that occur in a single day.
This is slightly faster that before, only at 20% of a full compile.