app_shell: build on any Linux, as there is no non-aura in the bot configurations.

Review URL: https://codereview.chromium.org/602293003

Cr-Commit-Position: refs/heads/master@{#297311}

build/all.gyp

@@ -253,7 +253,7 @@
             '../google_apis/gcm/gcm.gyp:*',
           ],
         }],
-        ['chromeos==1 or (OS=="linux" and use_aura==1) or OS=="win"', {
+        ['chromeos==1 or OS=="linux" or OS=="win"', {
           'dependencies': [
             '../extensions/shell/app_shell.gyp:*',
           ],