[CMake][Windows] Cleaner implementation of LLVM_TABLEGEN check

Author: wjristow

llvm/cmake/modules/TableGen.cmake

@@ -190,14 +190,14 @@ macro(add_tablegen target project)
   endif()
 
   # FIXME: Quick fix to reflect LLVM_TABLEGEN to llvm-min-tblgen
+  set(RAW_LLVM_TABLEGEN ${LLVM_TABLEGEN})
+  if(NOT "${RAW_LLVM_TABLEGEN}" STREQUAL "")
+    get_filename_component(RAW_LLVM_TABLEGEN ${RAW_LLVM_TABLEGEN} NAME_WE)
+  endif()
   if("${target}" STREQUAL "llvm-min-tblgen"
-      AND NOT "${LLVM_TABLEGEN}" STREQUAL "")
-    # Extract base filename from full path.
-    get_filename_component(RAW_LLVM_TABLEGEN ${LLVM_TABLEGEN} NAME_WE)
-    if(NOT "${RAW_LLVM_TABLEGEN}" STREQUAL ""
-        AND NOT "${RAW_LLVM_TABLEGEN}" STREQUAL "llvm-tblgen")
-      set(${project}_TABLEGEN_DEFAULT "${LLVM_TABLEGEN}")
-    endif()
+      AND NOT "${RAW_LLVM_TABLEGEN}" STREQUAL ""
+      AND NOT "${RAW_LLVM_TABLEGEN}" STREQUAL "llvm-tblgen")
+    set(${project}_TABLEGEN_DEFAULT "${LLVM_TABLEGEN}")
   endif()
 
   if(ADD_TABLEGEN_EXPORT)