Changes

debian: prepare for more subpackages

Prepare to add these subpackages in follow-up patches:
* osmocom-bb-trx-toolkit
* osmocom-bb-trxcon
* osmocom-bb-virtphy

We need these components to run some of the ttnc3 testsuites. By having
them packaged, we can just install them from the binary repositories
along with the SUT.

trxcon and virtphy are autootols based, so rework debian/rules to
support building multiple autotools projects.

Related: https://gerrit.osmocom.org/c/osmo-ttcn3-hacks/+/38851/1..2//COMMIT_MSG#b9
Change-Id: I77ad988f5405e6fa9e585eeb646e513ac7d92485