[test] Separate stdout and stderr in SwiftObjectNSObject.swift

remote-run doesn't always preserve the interleaving, but we don't need
stdout at all given what's being checked; it's just used to show how
far the test got before failing. The output being FileChecked is going
through NSLog, which uses stderr.

Part of rdar://problem/44866579

Author: jrose-apple

test/stdlib/SwiftObjectNSObject.swift

@@ -15,7 +15,8 @@
 // RUN: %target-clang %S/Inputs/SwiftObjectNSObject/SwiftObjectNSObject.m -c -o %t/SwiftObjectNSObject.o -g
 // RUN: %target-build-swift %s -I %S/Inputs/SwiftObjectNSObject/ -Xlinker %t/SwiftObjectNSObject.o -o %t/SwiftObjectNSObject
 // RUN: %target-codesign %t/SwiftObjectNSObject
-// RUN: %target-run %t/SwiftObjectNSObject 2>&1 | %FileCheck %s
+// RUN: %target-run %t/SwiftObjectNSObject 2> %t/log.txt
+// RUN: %FileCheck %s < %t/log.txt
 // REQUIRES: executable_test
 
 // REQUIRES: objc_interop