always build full reference slot for ci-test, closes #103
This should ensure that even when we launch
/ci-test --merge --platforms=x86_64_v2-centos7-gcc10-opt we still build all platforms for the reference slot.
This makes more sense as the full reference slot can be reused by following ci-test, and it avoids one particular annoying scenario:
/ci-test --merge --platforms=x86_64_v2-centos7-gcc10-opt
The above scenario needs only 1 full ref test, but currently this will result in 2 full ref builds + 1 ref build for the single platform.