Eliminate redundant Makefile variable (#1364)

Eliminate redundant variable

mlir/Makefile

@@ -15,7 +15,6 @@ BUILD_TYPE?=Release
 TARGET_FILE=$(MK_DIR)/mlir-hlo/mhlo/transforms/CMakeLists.txt
 PATCH_FILE=$(MK_DIR)/patches/mhlo-Add-PassesIncGen-in-transforms-CMakeList.patch
 LLVM_EXTERNAL_LIT ?= $(LLVM_BUILD_DIR)/bin/llvm-lit
-MLIR_DIR ?= $(shell pwd)/llvm-project/build/lib/cmake/mlir
 
 ifeq ($(shell uname), Darwin)
 DEFAULT_ENABLE_LLD := OFF
@@ -129,7 +128,7 @@ standalone-plugin:
 		patch -p0 < $(MK_DIR)/patches/test-plugin-with-catalyst.patch; \
 	fi
 	cmake -B standalone/build -G Ninja \
-		-DMLIR_DIR=$(MLIR_DIR) \
+		-DMLIR_DIR=$(LLVM_BUILD_DIR)/lib/cmake/mlir \
 		-DLLVM_EXTERNAL_LIT=$(LLVM_EXTERNAL_LIT) \
 		-DCATALYST_TOOLS_DIR=$(DIALECTS_BUILD_DIR)/bin \
 		-DPython3_EXECUTABLE=$(PYTHON) \