[Offload] Add OFFLOAD_INCLUDE_TESTS (#143388)

This is a cmake variable which, if set to `OFF` will disable building of
tests. It defaults to the value of `LLVM_INCLUDE_TESTS`.

offload/CMakeLists.txt

@@ -41,6 +41,8 @@ endif()
 
 set(LLVM_COMMON_CMAKE_UTILS ${CMAKE_CURRENT_SOURCE_DIR}/../cmake)
 
+option(OFFLOAD_INCLUDE_TESTS "Generate and build offload tests." ${LLVM_INCLUDE_TESTS})
+
 # Add path for custom modules
 list(INSERT CMAKE_MODULE_PATH 0
   "${CMAKE_CURRENT_SOURCE_DIR}/cmake"
@@ -376,15 +378,17 @@ add_subdirectory(libomptarget)
 add_subdirectory(liboffload)
 
 # Add tests.
-add_subdirectory(test)
+if(OFFLOAD_INCLUDE_TESTS)
+  add_subdirectory(test)
 
-# Add unit tests if GMock/GTest is present
-if(NOT LLVM_THIRD_PARTY_DIR)
+  # Add unit tests if GMock/GTest is present
+  if(NOT LLVM_THIRD_PARTY_DIR)
     set(LLVM_THIRD_PARTY_DIR "${CMAKE_CURRENT_SOURCE_DIR}/../third-party")
-endif()
-if(EXISTS ${LLVM_THIRD_PARTY_DIR}/unittest AND NOT TARGET llvm_gtest)
+  endif()
+  if(EXISTS ${LLVM_THIRD_PARTY_DIR}/unittest AND NOT TARGET llvm_gtest)
     add_subdirectory(${LLVM_THIRD_PARTY_DIR}/unittest ${CMAKE_CURRENT_BINARY_DIR}/third-party/unittest)
-endif()
-if(TARGET llvm_gtest)
+  endif()
+  if(TARGET llvm_gtest)
     add_subdirectory(unittests)
+  endif()
 endif()