debian-bookworm-titan: add ccache
Add ccache, so it can be used when rebuilding the testsuite from source
from a development branch. Ccache is not used by default.
Related: osmo-dev I800062d0379295a6905851db29e820ff16217653
Change-Id: I94d22b8da9f897974c5913b2a8138c653c215446
