[llvm] Reapply [MachO] Move getArchTriple implementation..." with fixes. (PR #161949)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `ppc64le-lld-multistage-test` running on `ppc64le-lld-multistage-test` while building `llvm` at step 7 "test-build-stage1-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/168/builds/16493

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 7 (test-build-stage1-unified-tree-check-all) failure: 1200 seconds without output running [b'ninja', b'check-all'], attempting to kill
...
llvm-lit: /home/buildbots/llvm-external-buildbots/workers/ppc64le-lld-multistage-test/ppc64le-lld-multistage-test/llvm-project/llvm/utils/lit/lit/llvm/config.py:530: note: using ld.lld: /home/buildbots/llvm-external-buildbots/workers/ppc64le-lld-multistage-test/ppc64le-lld-multistage-test/build/stage1/bin/ld.lld
llvm-lit: /home/buildbots/llvm-external-buildbots/workers/ppc64le-lld-multistage-test/ppc64le-lld-multistage-test/llvm-project/llvm/utils/lit/lit/llvm/config.py:530: note: using lld-link: /home/buildbots/llvm-external-buildbots/workers/ppc64le-lld-multistage-test/ppc64le-lld-multistage-test/build/stage1/bin/lld-link
llvm-lit: /home/buildbots/llvm-external-buildbots/workers/ppc64le-lld-multistage-test/ppc64le-lld-multistage-test/llvm-project/llvm/utils/lit/lit/llvm/config.py:530: note: using ld64.lld: /home/buildbots/llvm-external-buildbots/workers/ppc64le-lld-multistage-test/ppc64le-lld-multistage-test/build/stage1/bin/ld64.lld
llvm-lit: /home/buildbots/llvm-external-buildbots/workers/ppc64le-lld-multistage-test/ppc64le-lld-multistage-test/llvm-project/llvm/utils/lit/lit/llvm/config.py:530: note: using wasm-ld: /home/buildbots/llvm-external-buildbots/workers/ppc64le-lld-multistage-test/ppc64le-lld-multistage-test/build/stage1/bin/wasm-ld
llvm-lit: /home/buildbots/llvm-external-buildbots/workers/ppc64le-lld-multistage-test/ppc64le-lld-multistage-test/build/stage1/utils/lit/tests/lit.cfg:111: warning: Setting a timeout per test not supported. Requires the Python psutil module but it could not be found. Try installing it via pip or via your operating system's package manager.
 Some tests will be skipped and the --timeout command line argument will not work.
llvm-lit: /home/buildbots/llvm-external-buildbots/workers/ppc64le-lld-multistage-test/ppc64le-lld-multistage-test/llvm-project/llvm/utils/lit/lit/llvm/config.py:530: note: using ld.lld: /home/buildbots/llvm-external-buildbots/workers/ppc64le-lld-multistage-test/ppc64le-lld-multistage-test/build/stage1/bin/ld.lld
llvm-lit: /home/buildbots/llvm-external-buildbots/workers/ppc64le-lld-multistage-test/ppc64le-lld-multistage-test/llvm-project/llvm/utils/lit/lit/llvm/config.py:530: note: using lld-link: /home/buildbots/llvm-external-buildbots/workers/ppc64le-lld-multistage-test/ppc64le-lld-multistage-test/build/stage1/bin/lld-link
llvm-lit: /home/buildbots/llvm-external-buildbots/workers/ppc64le-lld-multistage-test/ppc64le-lld-multistage-test/llvm-project/llvm/utils/lit/lit/llvm/config.py:530: note: using ld64.lld: /home/buildbots/llvm-external-buildbots/workers/ppc64le-lld-multistage-test/ppc64le-lld-multistage-test/build/stage1/bin/ld64.lld
llvm-lit: /home/buildbots/llvm-external-buildbots/workers/ppc64le-lld-multistage-test/ppc64le-lld-multistage-test/llvm-project/llvm/utils/lit/lit/llvm/config.py:530: note: using wasm-ld: /home/buildbots/llvm-external-buildbots/workers/ppc64le-lld-multistage-test/ppc64le-lld-multistage-test/build/stage1/bin/wasm-ld
command timed out: 1200 seconds without output running [b'ninja', b'check-all'], attempting to kill
process killed by signal 9
program finished with exit code -1
elapsedTime=4623.673183
Testing:  0.. 10.. 20.. 30.. 40.. 50.. 60.. 70.. 80.. 90..
Step 12 (build-stage2-unified-tree) failure: build (failure) (timed out)
...
1121.758 [56/10/6654] Linking CXX executable bin/llvm-lto
1122.384 [56/9/6655] Linking CXX executable bin/llvm-reduce
1122.397 [56/8/6656] Linking CXX executable unittests/CodeGen/CGPluginTest/CGPluginTest
1122.404 [56/7/6657] Linking CXX executable bin/lld
1122.528 [56/6/6658] Linking CXX executable unittests/MI/MITests
1122.544 [56/5/6659] Linking CXX executable tools/lld/unittests/AsLibELF/LLDAsLibELFTests
1122.590 [56/4/6660] Linking CXX executable bin/clang-linker-wrapper
1122.667 [56/3/6661] Linking CXX executable bin/llc
1145.849 [56/2/6662] Building CXX object tools/bugpoint-passes/CMakeFiles/BugpointPasses.dir/TestPasses.cpp.o
1146.203 [55/2/6663] Linking CXX shared module lib/BugpointPasses.so
command timed out: 1200 seconds without output running [b'ninja'], attempting to kill
process killed by signal 9
program finished with exit code -1
elapsedTime=2347.014784

```

</details>

https://github.com/llvm/llvm-project/pull/161949