[clang] [llvm] [LLVM] Add GNU make jobserver support (PR #145131)

[LLVM Continuous Integration via cfe-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `clang-ppc64le-linux-test-suite` running on `ppc64le-clang-test-suite` while building `clang,llvm` at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/95/builds/18576

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

```
Step 6 (test-build-unified-tree-check-all) failure: test (failure)
******************** TEST 'LLVM-Unit :: Support/./SupportTests/582/1661' FAILED ********************
Script(shard):
--
GTEST_OUTPUT=json:/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-test-suite/clang-ppc64le-test-suite/build/unittests/Support/./SupportTests-LLVM-Unit-3588664-582-1661.json GTEST_SHUFFLE=0 GTEST_TOTAL_SHARDS=1661 GTEST_SHARD_INDEX=582 /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-test-suite/clang-ppc64le-test-suite/build/unittests/Support/./SupportTests
--


Note: This is test shard 583 of 1661.
[==========] Running 1 test from 1 test suite.
[----------] Global test environment set-up.
[----------] 1 test from JobserverStrategyTest
[ RUN      ] JobserverStrategyTest.ParallelSortIsLimited
[       OK ] JobserverStrategyTest.ParallelSortIsLimited (118 ms)
[----------] 1 test from JobserverStrategyTest (118 ms total)

[----------] Global test environment tear-down
[==========] 1 test from 1 test suite ran. (118 ms total)
[  PASSED  ] 1 test.

--
exit: -11
--

********************


```

</details>

https://github.com/llvm/llvm-project/pull/145131