Update lit.local.cfg

Author: makslevental

mlir/test/Examples/standalone/lit.local.cfg

@@ -10,3 +10,4 @@ config.substitutions.append(("%host_cc", config.host_cc))
 config.substitutions.append(("%enable_libcxx", config.enable_libcxx))
 config.substitutions.append(("%mlir_cmake_dir", config.mlir_cmake_dir))
 config.substitutions.append(("%llvm_use_linker", config.llvm_use_linker))
+config.substitutions.append(("%llvm_obj_root", config.llvm_obj_root))