dpkg: drop suffix from version number

dpkg: drop suffix from version number

The current dpkg runtime version is generated by 'git describe' command
in build-aux/get-version. But since we have made changes to git repo
locally, it adds a -dirty suffix to the version number.

Add a .dist-version file in the source directory. Then get-version can
determine the version through .dist-version instead of "git describe"
command, thus removing the -dirty suffix.

Before the fix:
$ dpkg --version
Debian 'dpkg' package management program version 1.22.11-dirty (amd64).

After the fix:
$ dpkg --version
Debian 'dpkg' package management program version 1.22.11 (amd64).

Signed-off-by: Yi Zhao <yi.zhao@windriver.com>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>