Enable viewer in non-Vulkan builds

tools/viewer/sk_app/unix/GLWindowContext_unix.cpp

 
 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GLWindowContext_unix.h"
 
@@ skipping 72 matching lines @@
         return;
     }
     glXMakeCurrent(fDisplay, None, nullptr);
     glXDestroyContext(fDisplay, fGLContext);
     fGLContext = nullptr;
 }
 
 
 void GLWindowContext_unix::onSwapBuffers() {
     if (fDisplay && fGLContext) {
-        printf("swapping\n");
         glXSwapBuffers(fDisplay, fWindow);
     }
 }
 
 
 }   //namespace sk_app