[OpenMP][omptest] Improve CMake and address review comments (#159416)

Avoid explicit ABI breaking check deactivation
Replace whole-archive linking with dedicated build of GoogleTest lib

Addresses remaining post-merge review comments of
https://github.com/llvm/llvm-project/pull/154786

openmp/tools/omptest/CMakeLists.txt

@@ -8,8 +8,7 @@ cmake_minimum_required(VERSION 3.20)
 project(omptest LANGUAGES CXX)
 
 option(LIBOMPTEST_BUILD_STANDALONE
-       "Build ompTest 'standalone', i.e. w/o GoogleTest."
-       ${OPENMP_STANDALONE_BUILD})
+       "Build ompTest 'standalone', i.e. w/o GoogleTest." OFF)
 option(LIBOMPTEST_BUILD_UNITTESTS
        "Build ompTest's unit tests, requires GoogleTest." OFF)
 option(LIBOMPTEST_INSTALL_COMPONENTS
@@ -20,6 +19,15 @@ if((NOT ${LIBOMP_OMPT_SUPPORT}) OR (NOT ${LLVM_INCLUDE_TESTS}))
   return()
 endif()
 
+# Only support OpenMP runtime 'bootstrap' build mode.
+# Check as seen in 'runtimes/CMakeLists.txt', due to passing HAVE_LLVM_LIT to
+# llvm_ExternalProject_Add() only.
+if (NOT HAVE_LLVM_LIT)
+  message(STATUS "Skipping omptest build. Reason: Only supported in bootstrap"
+                 " build mode of OpenMP runtime.")
+  return()
+endif()
+
 include(CMakePackageConfigHelpers)
 
 include_directories(${LIBOMP_INCLUDE_DIR})
@@ -51,7 +59,7 @@ add_library(omptest
 )
 
 # Target: ompTest library
-# On (implicit) request of GoogleTest, link against the one provided with LLVM.
+# On (implicit) request of GoogleTest, embed the sources provided with LLVM.
 if ((NOT LIBOMPTEST_BUILD_STANDALONE) OR LIBOMPTEST_BUILD_UNITTESTS)
   # Check if standalone build was requested together with unittests
   if (LIBOMPTEST_BUILD_STANDALONE)
@@ -65,34 +73,39 @@ if ((NOT LIBOMPTEST_BUILD_STANDALONE) OR LIBOMPTEST_BUILD_UNITTESTS)
     set(LIBOMPTEST_BUILD_STANDALONE OFF)
   endif()
 
-  # Add dependency llvm_gtest; emits error if unavailable.
-  add_dependencies(omptest llvm_gtest)
+  message(STATUS "omptest build mode: GTest-based")
 
-  # Link llvm_gtest as whole-archive to expose required symbols
-  set(GTEST_LINK_CMD "-Wl,--whole-archive" llvm_gtest
-                     "-Wl,--no-whole-archive" LLVMSupport)
+  # Add GoogleTest-based header and embed GTest symbols into the shared lib.
+  # Merging of GTest is desired, such that omptest is self-contained and
+  # independent of external GTest installations.
+  target_sources(omptest PRIVATE
+    $<TARGET_OBJECTS:default_gtest>
+  )
 
-  # Add GoogleTest-based header
-  target_sources(omptest PRIVATE ./include/OmptTesterGoogleTest.h)
+  # Link against the default GTest which at this point primarily pulls in the
+  # include directories and compile definitions. It is important to make these
+  # available to dependant targets, e.g. for unit tests.
+  target_link_libraries(omptest INTERFACE default_gtest)
 
-  # Add LLVM-provided GoogleTest include directories.
-  target_include_directories(omptest PRIVATE
-    ${LLVM_THIRD_PARTY_DIR}/unittest/googletest/include)
+  # Link against Threads (recommended for GTest).
+  find_package(Threads REQUIRED)
+  target_link_libraries(omptest PUBLIC Threads::Threads)
 
-  # TODO: Re-visit ABI breaking checks, disable for now.
-  target_compile_definitions(omptest PUBLIC
-    -DLLVM_DISABLE_ABI_BREAKING_CHECKS_ENFORCING)
-
-  # Link against gtest and gtest_main
-  target_link_libraries(omptest PRIVATE ${GTEST_LINK_CMD})
+  # Ensure that embedded GTest symbols are exported from libomptest.so even in
+  # builds that default to hidden.
+  set_target_properties(omptest PROPERTIES
+    CXX_VISIBILITY_PRESET default
+    VISIBILITY_INLINES_HIDDEN OFF
+  )
 else()
+  message(STATUS "omptest build mode: standalone")
+
   # Add 'standalone' compile definitions
   target_compile_definitions(omptest PRIVATE
     -DOPENMP_LIBOMPTEST_BUILD_STANDALONE)
 
   # Add 'standalone' source files
   target_sources(omptest PRIVATE
-    ./include/OmptTesterStandalone.h
     ./src/OmptTesterStandalone.cpp)
 endif()
 
@@ -138,7 +151,7 @@ if(LIBOMPTEST_INSTALL_COMPONENTS)
 
   # Install library and export targets.
   # Note: find_package(omptest) may require setting of PATH_SUFFIXES
-  #       Example: "lib/cmake/openmp/omptest", this is due to the install location
+  #       Example: "lib/cmake/openmp/omptest", due to the install location
   install(TARGETS omptest
           EXPORT OPENMPomptest
           LIBRARY COMPONENT omptest

openmp/tools/omptest/test/CMakeLists.txt

@@ -14,11 +14,8 @@ set(UNITTEST_SOURCES
 )
 add_executable(omptest-unittests ${UNITTEST_SOURCES})
 
-# Add local and LLVM-provided GoogleTest include directories.
-target_include_directories(omptest-unittests PRIVATE
-  ../include
-  ${LLVM_THIRD_PARTY_DIR}/unittest/googletest/include)
-
+# Add local include directory and link omptest library
+target_include_directories(omptest-unittests PRIVATE ../include)
 target_link_libraries(omptest-unittests PRIVATE omptest)
 
 set_target_properties(omptest-unittests PROPERTIES