build: correct linking to static libdispatch on Windows

When building against the static libdispatch, we need to inform the dispatch headers that the library will be linked statically via `-Ddispatch_STATIC`. Wire this up onto the dispatch library to allow `swiftDispatch` to properly propagate that flag.

Author: compnerd

src/CMakeLists.txt

@@ -95,6 +95,8 @@ target_include_directories(dispatch PRIVATE
 if(NOT BUILD_SHARED_LIBS)
  target_compile_definitions(dispatch PUBLIC
  dispatch_STATIC)
+ target_compile_options(dispatch PUBLIC
+ "$<$<COMPILE_LANGUAGE:Swift>:SHELL:-Xcc -Ddispatch_STATIC>")
 endif()
 if(WIN32)
  target_compile_definitions(dispatch PRIVATE