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

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.

Reviewed By: ChuanqiXu

Differential Revision: https://reviews.llvm.org/D126669