Silence some Win64 clang-cl warnings about unused stuff due to ifdefs

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@230685 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Support/Windows/Signals.inc

@@ -184,7 +184,8 @@ namespace llvm {
 /// AvoidMessageBoxHook - Emulates hitting "retry" from an "abort, retry,
 /// ignore" CRT debug report dialog.  "retry" raises an exception which
 /// ultimately triggers our stack dumper.
-static int AvoidMessageBoxHook(int ReportType, char *Message, int *Return) {
+static LLVM_ATTRIBUTE_UNUSED int
+AvoidMessageBoxHook(int ReportType, char *Message, int *Return) {
   // Set *Return to the retry code for the return value of _CrtDbgReport:
   // http://msdn.microsoft.com/en-us/library/8hyw4sy7(v=vs.71).aspx
   // This may also trigger just-in-time debugging via DebugBreak().

unittests/Support/CommandLineTest.cpp

@@ -35,6 +35,8 @@ class TempEnvVar {
 #if HAVE_SETENV
     // Assume setenv and unsetenv come together.
     unsetenv(name);
+#else
+    (void)name; // Suppress -Wunused-private-field.
 #endif
   }