[OPENMP]Fix a warning about unused variable, NFC.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@356715 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/CGOpenMPRuntimeNVPTX.cpp

@@ -4773,6 +4773,7 @@ Address CGOpenMPRuntimeNVPTX::getAddressOfLocalVariable(CodeGenFunction &CGF,
   // UseDefaultAllocator ? Address::invalid :
   // CGOpenMPRuntime::getAddressOfLocalVariable(CGF, VD); when NVPTX libomp
   // supports __kmpc_alloc|__kmpc_free.
+  (void)UseDefaultAllocator; // Prevent a warning.
   return Address::invalid();
 }