Add yasm to the GN build

BUILD.gn

 # Copyright (c) 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # This is the root build file for GN. GN will start processing by loading this
 # file, and recursively load all dependencies until all dependencies are either
 # resolved or known not to exist (which will cause the build to fail). So if
 # you add a new build file, there must be some path of dependencies from this
 # file to your new one or GN won't know about it.
 
@@ skipping 101 matching lines @@
     ]
   }
 
   if (is_win || is_mac || is_chromeos) {
     # RLZ works on these platforms.
     deps += [
       "//rlz:rlz_lib",
     ]
   }
 
+  if (cpu_arch == "x86" || cpu_arch == "x64") {
+    # YASM is x86/x64 only.
+    deps += [ "//third_party/yasm($host_toolchain)" ]
+  }
+
   if (is_android) {
     deps -= [
       "//cc",
       "//content/public/common",
       "//content/public/renderer",
       "//dbus",
       "//extensions/common/api:extensions_api",
       "//pdf",  # Not compiled on Android in GYP yet, either.
       "//ppapi:ppapi_c",
       "//sandbox",
@@ skipping 11 matching lines @@
     ]
   }
 
   if (use_ozone) {
     deps += [
       "//ui/events/ozone:events_ozone",
       "//ui/events/ozone:events_ozone_evdev",
     ]
   }
 }