Fixes problem with ubertooth-dfu not found. The install script assumes that ubertooth-dfu is already in the path. It is not when building the deb package, but it is available from a relative path since it has already been built.
When building the package, the source is not necessarily part of a git repository. This patch removes all git command executions. Additionally it replaces GIT_REVISION with the current Debian version number. This will go into some of the firmware files.
