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

[Rahul Joshi via llvm-commits]

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@@ -0,0 +1,5 @@
+add_lit_testsuite(check-llvm-unit "Running lit suite for LLVM unit tests"
+  ${CMAKE_CURRENT_BINARY_DIR}
+  EXCLUDE_FROM_CHECK_ALL
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jurahul wrote:

See similar PR for the earlier specialized suites: https://github.com/llvm/llvm-project/pull/159781

Without `EXCLUDE_FROM_CHECK_ALL`, these specialized test suites run twice, which is wasteful and sometimes leading to failure due to concurrent execution (which will likely not affect these unit tests).

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