util/release: Add support for signed tags and releases

* Add gpg key command-line parameter for signing.
* Add username command-line parameter for secure ssh clone.
* Tag and releases are signed.
* Generates ascii amored signature files.

Change-Id: I41347a85145dd0389e3b69939497fb8543db4996
Signed-off-by: Philipp Deppenwiese <zaolin@das-labor.org>
Reviewed-on: https://review.coreboot.org/16553
Tested-by: build bot (Jenkins)
Reviewed-by: Martin Roth <martinroth@google.com>
1 file changed