fix issue with multiple-target ant build http://codereview.appspot.com/6775056
fix issue with multiple-target ant build
http://codereview.appspot.com/6775056

'ant clean jars precajole' is broken and behaves differently from
'ant clean jars; ant precajole', because of the target Version.update.

Version.update checks if the output of svnversion has changed since
the last build, and removes a bunch of .js files to force them to
be regenerated with the new version string.

the problem is that properties in ant are immutable; once they're
set, their value can never be changed.

so when building the 'jars' target, the Version.changed property
is set to true, and then when continuing to the 'precajole' target
Version.changed is still true, even though we just built
everything with the right version string.  so during 'precajole',
the built files get removed again due to the misleading flag,
and 'precajole' has no dependencies that would cause those
removed files to be rebuilt again.

this CL fixes the issue by adding another flag so that Version.update
will never run more than once in a single ant invocation.

R=kpreid.switchb.org@gmail.com


git-svn-id: eb21526166532bd3afc2c1499c0cf105ce815f5a@5117 360991c0-9f3b-0410-ba87-8b362a00edf4

wishabi/caja-1,googlearchive/caja,googlearchive/caja,googlearchive/caja,initaldk/caja,cepm-nate/caja,jasvir/caja,wishabi/caja-1,cepm-nate/caja,jasvir/caja,jasvir/caja,googlearchive/caja,initaldk/caja,initaldk/caja,initaldk/caja,cepm-nate/caja,initaldk/caja,cepm-nate/caja,googlearchive/caja,googlearchive/caja,cepm-nate/caja,initaldk/caja,jasvir/caja,wishabi/caja-1,cepm-nate/caja,jasvir/caja,wishabi/caja-1,wishabi/caja-1,wishabi/caja-1,jasvir/caja