SNAPSHOTS_URL description appear to be out-of-date/irrelevant

http://bazaar.launchpad.net/~linaro-toolchain-dev/cbuild/trunk/view/head:/README describes SNAPSHOTS_URL as follows:

----------
If you want to build from a local
tarball, put that tarball in a directory and point SNAPSHOTS_URL at
it. Only .xz and .bz2 tarballs are supported.

Example:
 * Download gcc-4.7.1.tar.bz2
 * Put it in ~/tarballs
 * echo SNAPSHOTS_URL=~/tarballs >> local.mk
----------

However, setting SNAPSHOTS_URL=~/tarballs doesn't give the desired result - local mirror appears to be hardcoded as "$(TOPDIR)/tarballs".

Also, looking at makefiles, SNAPSHOTS_URL has default value of "orion::snapshots" and used only in contexts like:

rsync $(RSYNCFLAGS) $(SNAPSHOTS_URL)/$(@D)*z $(@D)