Fix crosssdk build on RISC-V

Remove gcc-sanitizers from the crosssdk when building for RISC-V, as
it is not currently supported on that platform.

Bug-AGL: SPEC-5116

Change-Id: If4e273c85b322f65635e2e9fc4752227f19b065c
Signed-off-by: Scott Murray <scott.murray@konsulko.com>
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/c/AGL/meta-agl-demo/+/29847
ci-image-boot-test: Jenkins Job builder account
Tested-by: Jenkins Job builder account
Reviewed-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>
ci-image-build: Jenkins Job builder account