Runtimes: use the static module constructor in swiftCore

Use the static module constructor for swiftCore on Windows as the
runtime functions are internal to the module. This fixes the last linker
warning that we see with the standard library build when building
dynamically. More importantly, this allows building swiftCore as a DLL
with the new build system on Windows as we now treat any linker warnings
as errors.

Author: compnerd

Runtimes/Core/core/CMakeLists.txt

@@ -306,7 +306,8 @@ target_link_libraries(swiftCore
     swiftDemangling
     swiftShims
     swiftStdlibStubs
-    swiftThreading)
+    swiftThreading
+    $<$<NOT:$<PLATFORM_ID:Darwin>>:swiftrt$<$<PLATFORM_ID:Windows>:T>>)
 target_link_options(swiftCore PRIVATE
   -nostartfiles)
 if(NOT POLICY CMP0157)