[XRay] Do not depend on C++ stdlib for XRay builds
[XRay] Do not depend on C++ stdlib for XRay builds

Summary:
Now that XRay doesn't require a runtime dependency on a C++ standard
library, we remove that dependency from the clang linker flags.

Reviewers: saugustine, pelikan

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D31313

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@298670 91177308-0d34-0410-b5e6-96231b3b80d8

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