Runtimes: create an Overlay project

This sets up the scaffolding for an Overlay project to allow building
platform specific overlays.

Author: compnerd

Runtimes/Overlay/CMakeLists.txt

@@ -0,0 +1,7 @@
+cmake_minimum_required(VERSION 3.26...3.29)
+
+project(SwiftOverlay LANGAUGES C VERSION 6.1)
+
+if(WIN32)
+  add_subdirectory(Windows)
+endif()

Runtimes/Overlay/Windows/CMakeLists.txt

@@ -0,0 +1,4 @@
+
+include(GNUInstallDirs)
+
+add_subdirectory(clang)

Runtimes/Overlay/Windows/clang/CMakeLists.txt

@@ -0,0 +1,7 @@
+
+install(FILES
+    ucrt.modulemap
+    vcruntime.apinotes
+    vcruntime.modulemap
+    winsdk.modulemap
+  DESTINATION ${CMAKE_INSTALL_PREFIX}/share)

Runtimes/Resync.cmake

@@ -68,7 +68,52 @@ file(COPY_FILE
   ONLY_IF_DIFFERENT)
 if(_output)
   message(SEND_ERROR
-    "Copy ${StdlibSources}/Info.plist.in] -> Core/Info.plist.in Failed: ${_output}")
+    "Copy ${StdlibSources}/Info.plist.in -> Core/Info.plist.in Failed: ${_output}")
+endif()
+
+# Copy Windows clang overlays
+message(STATUS "modulemap[${StdlibSources}/Windows/ucrt.modulemap] -> Overlay/Windows/clang")
+file(COPY_FILE
+  "${StdlibSources}/Platform/ucrt.modulemap"                        # From
+  "${CMAKE_CURRENT_LIST_DIR}/Overlay/Windows/clang/ucrt.modulemap"  # To
+  RESULT _output
+  ONLY_IF_DIFFERENT)
+if(_output)
+  message(SEND_ERROR
+    "Copy ${StdlibSources}/Platform/ucrt.modulemap -> Overlay/Windows/clang/ucrt.modulemap Failed: ${_output}")
+endif()
+
+message(STATUS "modulemap[${StdlibSources}/Windows/winsdk.modulemap] -> Overlay/Windows/clang")
+file(COPY_FILE
+  "${StdlibSources}/Platform/winsdk.modulemap"                        # From
+  "${CMAKE_CURRENT_LIST_DIR}/Overlay/Windows/clang/winsdk.modulemap"  # To
+  RESULT _output
+  ONLY_IF_DIFFERENT)
+if(_output)
+  message(SEND_ERROR
+    "Copy ${StdlibSources}/Platform/winsdk.modulemap -> Overlay/Windows/clang/winsdk.modulemap Failed: ${_output}")
+endif()
+
+message(STATUS "modulemap[${StdlibSources}/Windows/vcruntime.modulemap] -> Overlay/Windows/clang")
+file(COPY_FILE
+  "${StdlibSources}/Platform/vcruntime.modulemap"                       # From
+  "${CMAKE_CURRENT_LIST_DIR}/Overlay/Windows/clang/vcruntime.modulemap" # To
+  RESULT _output
+  ONLY_IF_DIFFERENT)
+if(_output)
+  message(SEND_ERROR
+    "Copy ${StdlibSources}/Platform/vcruntime.modulemap -> Overlay/Windows/clang/vcruntime.modulemap Failed: ${_output}")
+endif()
+
+message(STATUS "APINotes[${StdlibSources}/Windows/vcruntime.apinotes] -> Overlay/Windows/clang")
+file(COPY_FILE
+  "${StdlibSources}/Platform/vcruntime.apinotes"                        # From
+  "${CMAKE_CURRENT_LIST_DIR}/Overlay/Windows/clang/vcruntime.apinotes"  # To
+  RESULT _output
+  ONLY_IF_DIFFERENT)
+if(_output)
+  message(SEND_ERROR
+    "Copy ${StdlibSources}/Platform/vcruntime.apinotes -> Overlay/Windows/clang/vcruntime.modulemap Failed: ${_output}")
 endif()
 
 set(CoreLibs