[clang] [CIR] Minimize dependencies of check-clang-cir (PR #227957)

[Mehdi Amini via cfe-commits]

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@@ -238,11 +238,49 @@ add_lit_testsuite(check-clang "Running the Clang regression tests"
   ARGS ${CLANG_TEST_EXTRA_ARGS}
   )
 
+# Skip CIR here. check-clang above still discovers these tests, but they do
+# nothing unless CIR is enabled. When CIR is enabled, the check-clang-cir
+# targets below depend only on the tools those tests invoke and the tools
+# required to load clang/test/lit.cfg.py.
 add_lit_testsuites(CLANG ${CMAKE_CURRENT_SOURCE_DIR}
   DEPENDS ${CLANG_TEST_DEPS}
   FOLDER "Clang tests/Suites"
+  SKIP "^CIR"
----------------
joker-eph wrote:

```suggestion
  # This avoids automatically creating a `check-clang-cir` target for the CIR
  #  subdirectory, we create one explicitly below.
  SKIP "^CIR"
```

I think this can replace the comment above.  When I read "Skip CIR here" The first time, I thought it was skipping the tests, but then the explanation was confusing.

https://github.com/llvm/llvm-project/pull/227957