[CMake] Remove target to build native tablegen

[Hahnfeld]

Summary

This was once needed so that multiple tablegen binaries don't compile
the library concurrently. However, this isn't needed anymore since
adding USES_TERMINAL to the custom_command.
This is supported by the fact that the target was only building
LLVMSupport since some cleanups a year ago. If this dependency had
really been needed, we would have seen complaints.

[Hahnfeld]

Gentle ping

[beanz]

LGTM.

cmake/modules/TableGen.cmake

add_custom_target(${target}
     DEPENDS ${TABLEGEN_OUTPUT})
   if(LLVM_COMMON_DEPENDS)
     add_dependencies(${target} ${LLVM_COMMON_DEPENDS})
   endif()
   set_target_properties(${target} PROPERTIES FOLDER "Tablegenning")
   set(LLVM_COMMON_DEPENDS ${LLVM_COMMON_DEPENDS} ${target} PARENT_SCOPE)
 endfunction()
 
-if(LLVM_USE_HOST_TOOLS AND NOT TARGET NATIVE_LIB_LLVMTABLEGEN)
-  llvm_ExternalProject_BuildCmd(tblgen_build_cmd LLVMSupport
-    ${LLVM_NATIVE_BUILD}
-    CONFIGURATION Release)
-  add_custom_command(OUTPUT LIB_LLVMTABLEGEN
-      COMMAND ${tblgen_build_cmd}
-      DEPENDS CONFIGURE_LLVM_NATIVE
-      WORKING_DIRECTORY ${LLVM_NATIVE_BUILD}
-      COMMENT "Building libLLVMTableGen for native TableGen..."
-      USES_TERMINAL)
-  add_custom_target(NATIVE_LIB_LLVMTABLEGEN DEPENDS LIB_LLVMTABLEGEN)
-endif()
-
 macro(add_tablegen target project)
   set(${target}_OLD_LLVM_LINK_COMPONENTS ${LLVM_LINK_COMPONENTS})
   set(LLVM_LINK_COMPONENTS ${LLVM_LINK_COMPONENTS} TableGen)
 
   # CMake-3.9 doesn't let compilation units depend on their dependent libraries.
   if(NOT (CMAKE_GENERATOR STREQUAL "Ninja" AND NOT CMAKE_VERSION VERSION_LESS 3.9) AND NOT XCODE)
     # FIXME: It leaks to user, callee of add_tablegen.
     set(LLVM_ENABLE_OBJLIB ON)
if( ${${project}_TABLEGEN} STREQUAL "${target}" )
       endif()
       set(${project}_TABLEGEN_EXE ${${project}_TABLEGEN_EXE} PARENT_SCOPE)
 
       llvm_ExternalProject_BuildCmd(tblgen_build_cmd ${target}
                                     ${LLVM_NATIVE_BUILD}
                                     CONFIGURATION Release)
       add_custom_command(OUTPUT ${${project}_TABLEGEN_EXE}
         COMMAND ${tblgen_build_cmd}
-        DEPENDS ${target} NATIVE_LIB_LLVMTABLEGEN
+        DEPENDS CONFIGURE_LLVM_NATIVE ${target}
         WORKING_DIRECTORY ${LLVM_NATIVE_BUILD}
         COMMENT "Building native TableGen..."
         USES_TERMINAL)
       add_custom_target(${project}-tablegen-host DEPENDS ${${project}_TABLEGEN_EXE})
       set(${project}_TABLEGEN_TARGET ${project}-tablegen-host PARENT_SCOPE)
     endif()
   endif()