R1:bfdce02689b7

prepend path/to/phabricator/support/bin/ to $PATH

Summary:
It's sometimes necessary to specify the paths to individual binaries
explicitly, e.g. a particular build of 'javelinsymbols' or a newer
version of git than is installed on your shared system.

By adding symlinks in the .../phabricator/support/bin/ directory you
can now spell these out using the file system.

Test Plan:
Ran on local Ubuntu VM:

.. add 'TEST' repo to diffusion ..
.. visit 127.0.01/diffusion/TEST - see ok ..

$ cd /opt
$ sudo…