The dependencies are needed both at build time and at run time. Build
time needs them for running tests. To avoid duplicating the (long!)
list of dependencies, we do a little bit of trickery, and generate
a koha:Depends substvar, from all build dependencies (except debhelper),
and use ${koha:Depends} in the koha-common (not koha) Depends header.
A little bit tricky, but works.
Signed-off-by: Galen Charlton <gmcharlt@gmail.com>