Add new _foundation_unicode and _FoundationCShims c modules to windows build script (#74796)

* Add new _foundation_unicode and _FoundationCShims c modules to windows build script

* Only copy directories that exist

* Address feedback

Author: jmschonfeld

utils/build.ps1

@@ -1778,8 +1778,12 @@ function Install-Platform([Platform]$Platform, $Arch) {
   # Copy SDK header files
   Copy-Directory "$($Arch.SDKInstallRoot)\usr\include\swift\SwiftRemoteMirror" $SDKInstallRoot\usr\include\swift
   Copy-Directory "$($Arch.SDKInstallRoot)\usr\lib\swift\shims" $SDKInstallRoot\usr\lib\swift
-  foreach ($Module in ("Block", "dispatch", "os")) {
-    Copy-Directory "$($Arch.SDKInstallRoot)\usr\lib\swift\$Module" $SDKInstallRoot\usr\include
+  foreach ($Module in ("Block", "dispatch", "os", "_foundation_unicode", "_FoundationCShims")) {
+    $ModuleDirectory = "$($Arch.SDKInstallRoot)\usr\lib\swift\$Module"
+    $DestinationDirectory = "$SDKInstallRoot\usr\include"
+    if (Test-Path $ModuleDirectory) {
+      Copy-Directory $ModuleDirectory $DestinationDirectory
+    }
   }
 
   # Copy SDK share folder