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

This patch add CMake option "LLVM_GTEST_RUN_UNDER" to LLVM unittest
configuration. When specified, LLVM unittest will be run under the
wrapper program specified by this option. This feature can simplify the
setup to run LLVM unittest on a target platform that is different than
host.

llvm/CMakeLists.txt

@@ -1219,6 +1219,9 @@ if( LLVM_INCLUDE_EXAMPLES )
 endif()
 
 if( LLVM_INCLUDE_TESTS )
+  set(LLVM_GTEST_RUN_UNDER
+    "" CACHE STRING
+    "Define the wrapper program that LLVM unit tests should be run under.")
   if(EXISTS ${LLVM_MAIN_SRC_DIR}/projects/test-suite AND TARGET clang)
     include(LLVMExternalProjectUtils)
     llvm_ExternalProject_Add(test-suite ${LLVM_MAIN_SRC_DIR}/projects/test-suite

llvm/test/Unit/lit.cfg.py

@@ -19,7 +19,11 @@
 config.test_source_root = config.test_exec_root
 
 # testFormat: The test format to use to interpret tests.
-config.test_format = lit.formats.GoogleTest(config.llvm_build_mode, "Tests")
+config.test_format = lit.formats.GoogleTest(
+    config.llvm_build_mode,
+    "Tests",
+    run_under=config.gtest_run_under,
+)
 
 # Propagate the temp directory. Windows requires this because it uses \Windows\
 # if none of these are present.

llvm/test/Unit/lit.site.cfg.py.in

@@ -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@")
 
 # Let the main config do the real work.
 lit_config.load_config(