EISW-173753 Fix invalid TableGen flag in LLVM 20.x causing precommit failure

Exclude --no-warn-on-unused-template-args for mlir-src-sharder. This flag is not recognized by mlir-src-sharder and causes a build failure.
Exclude it conditionally while preserving it for other tools that support it.

Author: sramasit

llvm/cmake/modules/TableGen.cmake

@@ -80,8 +80,8 @@ function(tablegen project ofn)
     set(tblgen_change_flag "--write-if-changed")
   endif()
 
-  if (NOT LLVM_ENABLE_WARNINGS)
-    list(APPEND LLVM_TABLEGEN_FLAGS "-Dno-warn-on-unused-template-args")
+  if (NOT LLVM_ENABLE_WARNINGS AND NOT LLVM_TABLEGEN_EXE MATCHES "mlir-src-sharder")
+    list(APPEND LLVM_TABLEGEN_FLAGS "--no-warn-on-unused-template-args")
   endif()
 
   # We need both _TABLEGEN_TARGET and _TABLEGEN_EXE in the  DEPENDS list