handle errors in CI correctly

use && instead of ; to concatenate commands in Makefile so that errors (exit result 1) are handled properly

fixes one piece of a chain of issues which popped up after moving to proper imports of menshen dependencies (swagger client) in bitmask-core !38 (merged)

including menshen!57 (merged) and !39 (merged)

This MR ensures that we hopefully get noticed by the CI if cross-compiling of bitmask-core breaks due to upstream/dependency changes.

The failing build step https://0xacab.org/leap/bitmask-core/-/jobs/669612 proofes that. If we rebase this MR on top of !39 (merged) all lamps should be green again