WebAssembly: NFC fix release build break, unused variable.

Summary: Caused by D11914, pointed out by blaikie.

Subscribers: llvm-commits, jfb, dblaikie

Differential Revision: http://reviews.llvm.org/D11929

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@244570 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/WebAssembly/WebAssemblyAsmPrinter.cpp

@@ -126,6 +126,7 @@ void WebAssemblyAsmPrinter::EmitInstruction(const MachineInstr *MI) {
       auto Written =
           FP.convertToHexString(buf, /*hexDigits=*/0, /*upperCase=*/false,
                                 APFloat::rmNearestTiesToEven);
+      (void)Written;
       assert(Written != 0);
       assert(Written < BufBytes);
       OS << ' ' << buf;