[CMake][TableGen] Remove dead CMake version checks

LLVM requires CMake 3.13.4, so remove version checks that are dead code.

Reviewed By: phosek

Differential Revision: https://reviews.llvm.org/D87190

Author: tambry

llvm/cmake/modules/TableGen.cmake

@@ -8,9 +8,8 @@ function(tablegen project ofn)
     message(FATAL_ERROR "${project}_TABLEGEN_EXE not set")
   endif()
 
-  # Use depfile instead of globbing arbitrary *.td(s)
-  # DEPFILE is available for Ninja Generator with CMake>=3.7.
-  if(CMAKE_GENERATOR STREQUAL "Ninja" AND NOT CMAKE_VERSION VERSION_LESS 3.7)
+  # Use depfile instead of globbing arbitrary *.td(s) for Ninja.
+  if(CMAKE_GENERATOR STREQUAL "Ninja")
     # Make output path relative to build.ninja, assuming located on
     # ${CMAKE_BINARY_DIR}.
     # CMake emits build targets as relative paths but Ninja doesn't identify
@@ -134,8 +133,8 @@ macro(add_tablegen target project)
   set(${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)
+  # CMake doesn't let compilation units depend on their dependent libraries on some generators.
+  if(NOT CMAKE_GENERATOR STREQUAL "Ninja" AND NOT XCODE)
     # FIXME: It leaks to user, callee of add_tablegen.
     set(LLVM_ENABLE_OBJLIB ON)
   endif()