[llvm] [NFC][LLVM-Tests] Specialize test suite for LLVM unit tests (PR #161442)

[Rahul Joshi via llvm-commits]

jurahul wrote:

Ok. in the latest test PR version, I do see that the 2 faulty unit tests do fail:

```
FAIL: LLVM-Unit :: Support/./SupportTests/34/104 (8615 of 61658)
******************** TEST 'LLVM-Unit :: Support/./SupportTests/34/104' FAILED ********************
Script(shard):
--
GTEST_OUTPUT=json:/home/gha/actions-runner/_work/llvm-project/llvm-project/build/unittests/Support/./SupportTests-LLVM-Unit-1199807-34-104.json GTEST_SHUFFLE=0 GTEST_TOTAL_SHARDS=104 GTEST_SHARD_INDEX=34 /home/gha/actions-runner/_work/llvm-project/llvm-project/build/unittests/Support/./SupportTests
--
Script:
--
/home/gha/actions-runner/_work/llvm-project/llvm-project/build/unittests/Support/./SupportTests --gtest_filter=CastingTest.isa
--
Classof: 0xa741f0
/home/gha/actions-runner/_work/llvm-project/llvm-project/llvm/unittests/Support/Casting.cpp:151: Failure
Value of: isa<foo>(B1)
  Actual: true
Expected: false
Classof: 0xa741f0
Classof: 0xa741f0
Classof: 0xa741f0
/home/gha/actions-runner/_work/llvm-project/llvm-project/llvm/unittests/Support/Casting.cpp:151
Value of: isa<foo>(B1)
  Actual: true
Expected: false
********************
Testing:  0.. 10.. 20.. 30.. 40.. 50.. 60.. 70.. 80.. 90.
FAIL: LLVM-Unit :: IR/./IRTests/90/103 (42923 of 61658)
******************** TEST 'LLVM-Unit :: IR/./IRTests/90/103' FAILED ********************
```

https://github.com/llvm/llvm-project/pull/161442