[unittests] Use object library if cmake supports it

Differential Revision: https://reviews.llvm.org/D63544

llvm-svn: 363933

lldb/unittests/tools/lldb-mi/utils/CMakeLists.txt

@@ -1,4 +1,10 @@
-add_library(lldb-mi-utils OBJECT
+# Create object library to avoid unnecessary linking. If CMake version
+# doesn't support it, just create an ordinary library.
+if(NOT (${CMAKE_VERSION} VERSION_LESS "3.5.0"))
+  set (LIBRARY_TYPE "OBJECT")
+endif()
+
+add_library(lldb-mi-utils ${LIBRARY_TYPE}
   ${LLDB_SOURCE_DIR}/tools/lldb-mi/MIUtilString.cpp
   )
 
@@ -9,5 +15,16 @@ add_lldb_unittest(LLDBMiUtilTests
     Support
   )
 
-target_sources(LLDBMiUtilTests PRIVATE $<TARGET_OBJECTS:lldb-mi-utils>)
+if((${CMAKE_VERSION} VERSION_LESS "3.5.0") OR
+    NOT (${CMAKE_VERSION} VERSION_LESS "3.12.0"))
+  # Link to either usual (cmake version < 3.5) or
+  # object (cmake version >= 3.12) library with lldm-mi sources.
+  target_link_libraries(LLDBMiUtilTests PRIVATE lldb-mi-utils)
+else()
+  # Object libraries still cannot be on the right-hand side of
+  # `target_link_libraries` but `$<TARGET_OBJECTS:objlib>` expression is
+  # already supported in `target_sources`.
+  target_sources(LLDBMiUtilTests PRIVATE $<TARGET_OBJECTS:lldb-mi-utils>)
+endif()
+
 set_target_properties(lldb-mi-utils PROPERTIES FOLDER "lldb libraries")