JettyDaemon invokes buck build to ensure GWT JS is up-to-date before
running the server. To be completely compatible with the command line
build it uses the same PATH environment variable, ignoring the PATH
that is inherited from Eclipse.
Including the PATH as part of the genrule() command ensures buck will
rewrite the properties file anytime the user modifies the PATH, rather
than only when there are updates to GWT Java sources.
Using a properties file frees us from worrying about double quoting in
shell: once in the genrule, again in the script itself.
Using a single properties file ensures any GWT UI can be computed or
verified by JettyDaemon. This change simplifies bootstrap for a
developer as they no longer need to build the UI before launching the
server from within Eclipse. JettyDaemon now takes care of it.
Change-Id: If096a60d9a3f9d6d1502cc947b966109b4458717
6dec5bf32e