This change allows the user to select if he wants to sign the patch
using the SIGN_PATCH variable, when set to True it will automatically
add the "--remote-sign" option to the patch-builder script and export
the env variables, SIGNING_USER and SIGNING_SERVER, from the build.conf
Test plan:
PASS: Run entire patch pipeline with SIGN_PATCH enable
Story: 2010676
Task: 51404
Change-Id: I7e895f30ea64a517a3555117250a4f00f8b6dfe1
Signed-off-by: Dostoievski Batista <dostoievski.albinobatista@windriver.com>