lldb: Disable unittests if llvm_gtest target does not exist

[tstellar]

Summary

This fixes the stand-alone build configuration where LLVM_MAIN_SRC_DIR
does not exist.

[JDevlieghere]

Could this go in LLDBStandalone.cmake?

[tstellar]

Move new logic to LLDBStandalone.cmake

[JDevlieghere]

LGTM

[mgorny]

Unfortunately, this change doesn't work correctly when building LLDB through LLVM_ENABLE_PROJECTS — unittests are always disabled now.

lldb/CMakeLists.txt

128 ↗

(On Diff #451684)

If LLDB is built through LLVM_ENABLE_PROJECTS, then LLDB's CMakeLists are included before the subdirectory containing llvm_gtest, effectively making this condition always false.

[JDevlieghere]

lldb/CMakeLists.txt

128 ↗

(On Diff #451684)

Good catch. I've put up https://reviews.llvm.org/D131861 as a (straw man) proposal. But I haven't tested it yet.

llvm/CMakeLists.txt

 if( LLVM_INCLUDE_UTILS )
   add_subdirectory(utils/FileCheck)
   add_subdirectory(utils/PerfectShuffle)
   add_subdirectory(utils/count)
   add_subdirectory(utils/not)
   add_subdirectory(utils/UnicodeData)
   add_subdirectory(utils/yaml-bench)
   add_subdirectory(utils/split-file)
+  if( LLVM_INCLUDE_TESTS )
+    add_subdirectory(utils/unittest)
+  endif()
 else()
   if ( LLVM_INCLUDE_TESTS )
     message(FATAL_ERROR "Including tests when not building utils will not work.
     Either set LLVM_INCLUDE_UTILS to On, or set LLVM_INCLUDE_TESTS to Off.")
   endif()
 endif()
 
 # Use LLVM_ADD_NATIVE_VISUALIZERS_TO_SOLUTION instead of LLVM_INCLUDE_UTILS because it is not really a util
llvm_ExternalProject_Add(test-suite ${LLVM_MAIN_SRC_DIR}/projects/test-suite
       USE_TOOLCHAIN
       EXCLUDE_FROM_ALL
       NO_INSTALL
       ALWAYS_CLEAN)
   endif()
   add_subdirectory(utils/lit)
   add_subdirectory(test)
   add_subdirectory(unittests)
-  if( LLVM_INCLUDE_UTILS )
-    add_subdirectory(utils/unittest)
-  endif()
 
   if (WIN32)
     # This utility is used to prevent crashing tests from calling Dr. Watson on
     # Windows.
     add_subdirectory(utils/KillTheDoctor)
   endif()
 
   umbrella_lit_testsuite_end(check-all)