I found something about sign in release ENV，but how ? below is the description in your demo（custom_rules.xml）:
release: Builds the application. The generated apk file must be
signed before it is published.
The 'nodeps' target can be used to only build the
current project and ignore the libraries using:
'ant nodeps release'

PLS help me: How to use this command signature.(I already have a signature file)