Revert "Build workaround: only consider shims to be protected in Swift code on Darwin."

This reverts commit 3e20817.  Now that we are
using gold, this should work.  The work around is only needed for BFD linkers.

Author: compnerd

cmake/modules/SwiftSource.cmake

@@ -79,8 +79,7 @@ function(handle_swift_sources
     # <rdar://problem/15972329>
     list(APPEND swift_compile_flags "-force-single-frontend-invocation")
 
-    # FIXME: Apply this on all platforms where the linker supports it.
-    if(SWIFTSOURCES_IS_STDLIB_CORE AND "${CMAKE_SYSTEM_NAME}" STREQUAL "Darwin")
+    if(SWIFTSOURCES_IS_STDLIB_CORE)
       list(APPEND swift_compile_flags "-Xcc" "-D__SWIFT_CURRENT_DYLIB=swiftCore")
     endif()