[Driver][Modules] Remove dependence on linking support from clang/test/Driver/modules.cpp

[DanielMcIntosh-IBM]

Summary

The new tests in clang/test/Driver/modules.cpp added by D120540 will fail if the
toolchain getting tested doesn't support linking. This reduces the utility of
the test since we would like a failure of this test to reflect a problem with
modules. We should already have other tests that validate linking support.

[MaskRay]

This change is fine (if I were adding the tests in the first place, I'd add -c or -S), but I'd like to understand why you have such a toolchain not supporting linking.
Such special requirements make me feel odd.

[DanielMcIntosh-IBM]

In D126669#3546172, @MaskRay wrote:

This change is fine (if I were adding the tests in the first place, I'd add -c or -S), but I'd like to understand why you have such a toolchain not supporting linking.
Such special requirements make me feel odd.

Downstream we have a branch that only contains some of the required changes for z/OS support, but which we still run tests on (why this is the case is a long story, but it's something we're working on fixing, it's just going to take a very long time to do so). This test is failing on that branch. Rather than loose the test, I figured I'd improve the test and in the process get it working again on that branch.

[ChuanqiXu]

LGTM

clang/test/Driver/modules.cpp

 import "foo.h";
 
 // CHECK-HEADER-UNIT-USE: BAR;
 FOO;
 #endif
 
 // Check the independent use of -fcxx-modules
 //
-// RUN: %clang -fcxx-modules -std=c++17 -### %s 2>&1 | FileCheck %s --check-prefix=CHECK-CXX17-MODULES
-// CHECK-CXX17-MODULES: "-fcxx-modules"
-// RUN: %clang -fcxx-modules -std=c++14 -### %s 2>&1 | FileCheck %s --check-prefix=CHECK-CXX14-MODULES
-// CHECK-CXX14-MODULES: "-fcxx-modules"
-// RUN: %clang -fcxx-modules -std=c++11 -### %s 2>&1 | FileCheck %s --check-prefix=CHECK-CXX11-MODULES
-// CHECK-CXX11-MODULES: "-fcxx-modules"
-// RUN: %clang -fcxx-modules -std=c++03 -### %s 2>&1 | FileCheck %s --check-prefix=CHECK-CXX03-MODULES
-// CHECK-CXX03-MODULES: "-fcxx-modules"
+// RUN: %clang -fcxx-modules -std=c++17 -### -c %s 2>&1 | FileCheck %s --check-prefix=CHECK-CXX-MODULES
+// RUN: %clang -fcxx-modules -std=c++14 -### -c %s 2>&1 | FileCheck %s --check-prefix=CHECK-CXX-MODULES
+// RUN: %clang -fcxx-modules -std=c++11 -### -c %s 2>&1 | FileCheck %s --check-prefix=CHECK-CXX-MODULES
+// RUN: %clang -fcxx-modules -std=c++03 -### -c %s 2>&1 | FileCheck %s --check-prefix=CHECK-CXX-MODULES
+// CHECK-CXX-MODULES: "-fcxx-modules"