[GTK] Export the COLLECT_NO_DEMANGLE variable on the builders
https://bugs.webkit.org/show_bug.cgi?id=115323

Reviewed by Philippe Normand.

Export the COLLECT_NO_DEMANGLE environment variable on the GTK BuildBot builders.
Its presence enforces linkers to output mangled symbols when reporting linking failures
due to unresolved references. People trying to fix the build can then simply copy
the printed mangled symbol into the symbols.filter file instead of doing a manual build
or connecting to the builders to discover the mangled version of the missing symbol.

* BuildSlaveSupport/gtk/daemontools-buildbot.conf:


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@149271 268f45cc-cd09-0410-ab3c-d52691b4dbfc