[MC] Silence warning due to unused variable in !Debug builds.

llvm-svn: 266901
diff --git a/llvm/lib/Target/X86/X86MCInstLower.cpp b/llvm/lib/Target/X86/X86MCInstLower.cpp
index 6b42943..6fc73aa 100644
--- a/llvm/lib/Target/X86/X86MCInstLower.cpp
+++ b/llvm/lib/Target/X86/X86MCInstLower.cpp
@@ -838,6 +838,7 @@
 static void EmitNops(MCStreamer &OS, unsigned NumBytes, bool Is64Bit,
                      const MCSubtargetInfo &STI) {
   unsigned NopsToEmit = NumBytes;
+  (void)NopsToEmit;
   while (NumBytes) {
     NumBytes -= EmitNop(OS, NumBytes, Is64Bit, STI);
     assert(NopsToEmit >= NumBytes && "Emitted more than I asked for!");