Correct VFS libc modulemap injection condition.
Correct VFS libc modulemap injection condition.

We should only be skipping VFS libc modulemap injection on Darwin and
Windows. Unfortunately, we cannot just use the isOSGlibc Triple method
because LLVM's sense of Glibc (does the platform _actually use_ glibc)
differs from Swift's sense of Glibc (does the platform use libc).

There may be other non-libc platforms that we should skip VFS injection
on but let's correct the conditional for now and other prs should add
those platforms as necessary.

roambotics/swift,roambotics/swift,benlangmuir/swift,benlangmuir/swift,roambotics/swift,apple/swift,roambotics/swift,apple/swift,roambotics/swift,apple/swift,glessard/swift,apple/swift,apple/swift,benlangmuir/swift,glessard/swift,roambotics/swift,glessard/swift,glessard/swift,glessard/swift,benlangmuir/swift,benlangmuir/swift,apple/swift,benlangmuir/swift,glessard/swift