chore: use hermetic awk for mtree manipulation

[alexeagle]

Testing locally isn't working on MacOS arm64:

ERROR: /private/var/tmp/_bazel_alexeagle/ac5c25dfb9cf2a4fcbea5ab9eb6f568e/external/gawk/BUILD.bazel:52:11: Linking external/gawk/libsupport.a [for tool] failed: (Exit 1): llvm-ar failed: error executing CppArchive command (from target @@gawk//:support) external/llvm_toolchain/bin/llvm-ar @bazel-out/darwin_arm64-opt-exec-ST-a828a81199fe/bin/external/gawk/libsupport.a-2.params

Use --sandbox_debug to see verbose messages from the sandbox and retain the sandbox build root for debugging
external/llvm_toolchain/bin/llvm-ar: error: only one operation may be specified
OVERVIEW: LLVM Archiver

[github-actions]

e2e/use_release folder: LCOV of commit 437ba48 during CI #1989

Summary coverage rate:
  lines......: 100.0% (2 of 2 lines)
  functions..: 100.0% (1 of 1 function)
  branches...: no data found

Files changed coverage rate: n/a

[aspect-workflows]

Test

7 test targets passed

Targets

//py/tests/py_image_layer:my_app_layers_test_test [k8-fastbuild]                          44ms
//py/tests/py_image_layer:py_image_test [k8-fastbuild]                                    4s
//py/tests/py_venv_image_layer:my_app_amd64_layers_test [k8-fastbuild]                    100ms
//py/tests/py_venv_image_layer:my_app_arm64_layers_test [k8-fastbuild]                    48ms
//py/tests/py_venv_image_layer:py_amd64_image_command_test [k8-fastbuild]                 6s
//py/tests/py_venv_image_layer:py_amd64_image_content_test [k8-fastbuild]                 269ms
//py/tests/py_venv_image_layer:py_arm64_image_content_test [k8-fastbuild]                 2s

Total test execution time was 12s. 38 tests (84.4%) were fully cached saving 1m 14s.

[UebelAndre]

I will take a look at the build issue separately but the changes otherwise seem fine to me 😄