[flang] Fix buildbot failure after #152914 (#153578)

Buildbot failure:
https://lab.llvm.org/buildbot/#/builders/201/builds/5894

flang/test/Integration/iso-fortran-binding.cpp

@@ -1,17 +1,9 @@
 // REQUIRES: clang
 // UNSUPPORTED: system-windows
-// RUN: rm -rf %t && mkdir %t
-// RUN: %clangxx %isysroot -I%flang_include %s -o %t/a.out
-// RUN: %t/a.out | FileCheck %s
+// RUN: %clang_cc1 -fsyntax-only -I%flang_include %s -x c++
 
 extern "C" {
 #include "ISO_Fortran_binding.h"
 }
-#include <iostream>
 
-int main() {
-  std::cout << "PASS\n";
-  return 0;
-}
-
-// CHECK: PASS
+int main() { return 0; }