swift

164ac421 - Sema: Lift restriction preventing use of `#_hasSymbol` on non-Darwin platforms.

Sema: Lift restriction preventing use of `#_hasSymbol` on non-Darwin platforms. An early approach to codegen for `#_hasSymbol` relied on the Darwin platfom SDK, but now that the feature lowers directly to NULL checks in LLVM IR a platform restriction is no longer needed. However, the tests for `#_hasSymbol` remain unsupported on Windows since that OS does not support weak linking.