[XcodeGen] Make 'Byte' comform 'ExpressibleByUnicodeScalarLiteral'

Instead of comparing with 'UnicodeScalar', construct 'Byte' from
literals and compare with them. Make it less evil :)

utils/swift-xcodegen/Sources/SwiftXcodeGen/Utils.swift

@@ -78,7 +78,7 @@ extension String {
       let result = scanner.consumeWhole { consumer in
         switch consumer.peek {
         case "\\", "\"":
-          consumer.append(Byte(ascii: "\\"))
+          consumer.append("\\")
         case " ", "$": // $ is potentially a variable reference
           needsQuotes = true
         default: