Merge pull request #12246 from linux-on-ibm-z/swift40-URBPTest-fix

[stdlib] Fix for initFromArray test on big endian (4.0)

Author: moiseev

test/stdlib/UnsafeRawBufferPointer.swift

@@ -66,7 +66,11 @@ UnsafeRawBufferPointerTestSuite.test("initFromArray") {
   array1.withUnsafeBytes { bytes1 in
     expectEqual(bytes1.count, 16)
     for (i, b) in bytes1.enumerated() {
-      if i % 4 == 0 {
+      var num = i
+#if _endian(big)
+      num = num + 1
+#endif
+      if num % 4 == 0 {
         expectEqual(Int(b), i / 4)
       }
       else {