[CMake] OBJLIB-ize *-tblgen.

This improves dependency chain of;

  (LLVMSupport && LLVMTableGen) && (*.cpp in *-tblgen) && (linking *-tblgen)

with;

  (LLVMSupport && LLVMTableGen && *.cpp) && (linking *-tblgen)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@246156 91177308-0d34-0410-b5e6-96231b3b80d8

cmake/modules/AddLLVM.cmake

@@ -565,6 +565,19 @@ macro(add_llvm_executable name)
   llvm_process_sources( ALL_FILES ${ARGN} )
   add_windows_version_resource_file(ALL_FILES ${ALL_FILES})
 
+  # Generate objlib
+  if(LLVM_ENABLE_OBJLIB)
+    # Generate an obj library for both targets.
+    set(obj_name "obj.${name}")
+    add_library(${obj_name} OBJECT EXCLUDE_FROM_ALL
+      ${ALL_FILES}
+      )
+    llvm_update_compile_flags(${obj_name})
+    set(ALL_FILES "$<TARGET_OBJECTS:${obj_name}>")
+
+    set_target_properties(${obj_name} PROPERTIES FOLDER "Object Libraries")
+  endif()
+
   if( EXCLUDE_FROM_ALL )
     add_executable(${name} EXCLUDE_FROM_ALL ${ALL_FILES})
   else()

cmake/modules/TableGen.cmake

@@ -73,6 +73,10 @@ endfunction()
 macro(add_tablegen target project)
   set(${target}_OLD_LLVM_LINK_COMPONENTS ${LLVM_LINK_COMPONENTS})
   set(LLVM_LINK_COMPONENTS ${LLVM_LINK_COMPONENTS} TableGen)
+
+  # FIXME: It leaks to user, callee of add_tablegen.
+  set(LLVM_ENABLE_OBJLIB ON)
+
   add_llvm_utility(${target} ${ARGN})
   set(LLVM_LINK_COMPONENTS ${${target}_OLD_LLVM_LINK_COMPONENTS})