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

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `clang-armv8-quick` running on `linaro-clang-armv8-quick` while building `clang,llvm` at step 5 "ninja check 1".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/154/builds/22292

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

```
Step 5 (ninja check 1) failure: stage 1 checked (failure)
******************** TEST 'LLVM-Unit :: Support/./SupportTests/165/415' FAILED ********************
Script(shard):
--
GTEST_OUTPUT=json:/home/tcwg-buildbot/worker/clang-armv8-quick/stage1/unittests/Support/./SupportTests-LLVM-Unit-1361811-165-415.json GTEST_SHUFFLE=0 GTEST_TOTAL_SHARDS=415 GTEST_SHARD_INDEX=165 /home/tcwg-buildbot/worker/clang-armv8-quick/stage1/unittests/Support/./SupportTests
--


Note: This is test shard 166 of 415.
[==========] Running 4 tests from 4 test suites.
[----------] Global test environment set-up.
[----------] 1 test from CheckedArithmetic
[ RUN      ] CheckedArithmetic.CheckedAddUnsigned
[       OK ] CheckedArithmetic.CheckedAddUnsigned (0 ms)
[----------] 1 test from CheckedArithmetic (0 ms total)

[----------] 1 test from JobserverStrategyTest
[ RUN      ] JobserverStrategyTest.ParallelForIsLimited
[       OK ] JobserverStrategyTest.ParallelForIsLimited (214 ms)
[----------] 1 test from JobserverStrategyTest (214 ms total)

[----------] 1 test from ProgramEnvTest
[ RUN      ] ProgramEnvTest.TestLockFileExclusive
Note: Google Test filter = ProgramEnvTest.TestLockFileExclusive
[==========] Running 1 test from 1 test suite.
[----------] Global test environment set-up.
[----------] 1 test from ProgramEnvTest
[ RUN      ] ProgramEnvTest.TestLockFileExclusive
../llvm/llvm/unittests/Support/ProgramTest.cpp:594: Failure
Value of: fs::tryLockFile(FD2, std::chrono::seconds(0), fs::LockKind::Shared)
  Actual: true
Expected: false

[       OK ] ProgramEnvTest.TestLockFileExclusive (55 ms)
[----------] 1 test from ProgramEnvTest (55 ms total)

[----------] 1 test from YAMLIO
[ RUN      ] YAMLIO.TestReadBuiltInTypesint8OverError
[       OK ] YAMLIO.TestReadBuiltInTypesint8OverError (0 ms)
[----------] 1 test from YAMLIO (0 ms total)

[----------] Global test environment tear-down
[==========] 4 tests from 4 test suites ran. (270 ms total)
[  PASSED  ] 4 tests.

--
exit: -11
--

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


```

</details>

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