[llvm] [unittest] Allow LLVM unit test to run under a wrapper program. (PR #66821)

[Petr Hosek via llvm-commits]

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@@ -7,6 +7,7 @@ config.llvm_obj_root = path(r"@LLVM_BINARY_DIR@")
 config.llvm_tools_dir = lit_config.substitute(path(r"@LLVM_TOOLS_DIR@"))
 config.llvm_build_mode = lit_config.substitute("@LLVM_BUILD_MODE@")
 config.shlibdir = lit_config.substitute(path(r"@SHLIBDIR@"))
+config.gtest_run_under = lit_config.substitute(r"@LLVM_GTEST_RUN_UNDER@")
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petrhosek wrote:

Can you set this variable in `llvm/CMakeLists.txt" as a cached value, defaulting to an empty string and providing a short description?

https://github.com/llvm/llvm-project/pull/66821