[GTK] Create a wrapper script that knows how to install jhbuild and run commands...

[GTK] Create a wrapper script that knows how to install jhbuild and run commands with it
https://bugs.webkit.org/show_bug.cgi?id=73669

Reviewed by Gustavo Noronha Silva.

Add a wrapper script that knows how to install jhbuild and also to wrap commands
in the jhbuild shell.

* Scripts/webkitdirs.pm:
(runAutogenForAutotoolsProject): Use the new wrapper script.
(mustReRunAutogen): Ditto.
(buildAutotoolsProject): Ditto.
* Scripts/webkitpy/layout_tests/port/gtk.py:
(GtkDriver.cmd_line): Ditto.
* gtk/run-with-jhbuild: Added.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@101814 268f45cc-cd09-0410-ab3c-d52691b4dbfc