Fix String.init test in FixedPoint.swift.gyb for big-endian systems.

Author: Gary Liu

validation-test/stdlib/FixedPoint.swift.gyb

@@ -307,10 +307,17 @@ FixedPoint.test("OverflowCheck") {
 
 FixedPoint.test("String.init") {
   let x: UInt32 = 0xdeadbeef
+#if _endian(little)
   expectEqual("efbeadde", String(x.bigEndian, radix: 16))
 
   let y = UInt32(bigEndian: 0xdeadbeef)
   expectEqual("deadbeef", String(y.bigEndian, radix: 16))
+#else
+  expectEqual("efbeadde", String(x.littleEndian, radix: 16))
+
+  let y = UInt32(littleEndian: 0xdeadbeef)
+  expectEqual("deadbeef", String(y.littleEndian, radix: 16))
+#endif
 }
 
 FixedPoint.test("byteSwapped") {
@@ -426,5 +433,4 @@ BoolTestSuite.test("||") {
   expectFalse(getBool(false) || getBool(false))
 }
 
-runAllTests()
-
+runAllTests()