[NOUPSTREAM] CI: disable RELR

The arm64 binutils from Debian testing generate non working
RELR code resulting in a non-booting kernel. As a workaround
disable RELR to get a booting kernel. This can be reverted
once Debian's binutils are fixed. More information are available
in this bug report:

https://bugs.debian.org/1074111



Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>