Expose DEPLOYMENT_POSTPROCESSING in ProjectModel.BuildSettings

Requested to be used in swiftlang/swift-package-manager#9380

Author: svmkr-dev

Sources/SwiftBuild/ProjectModel/BuildSettings.swift

@@ -29,6 +29,7 @@ extension ProjectModel {
             case COPY_PHASE_STRIP
             case DEBUG_INFORMATION_FORMAT
             case DEFINES_MODULE
+            case DEPLOYMENT_POSTPROCESSING
             case DRIVERKIT_DEPLOYMENT_TARGET
             case DYLIB_INSTALL_NAME_BASE
             case EMBEDDED_CONTENT_CONTAINS_SWIFT