[CIR] Fix test to use -emit-mlir=core

Author: bcardosolopes

clang/test/CIR/Lowering/ThroughMLIR/array.c

@@ -1,6 +1,6 @@
 // RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -fclangir -emit-cir %s -o %t.cir
 // RUN: FileCheck --input-file=%t.cir %s --check-prefix=CIR
-// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -fclangir -fno-clangir-direct-lowering -emit-mlir %s -o %t.mlir
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -fclangir -fno-clangir-direct-lowering -emit-mlir=core %s -o %t.mlir
 // RUN: FileCheck --input-file=%t.mlir %s --check-prefix=MLIR
 
 int test_array1() {