Você está procurando override_dh_build-indep
na página de manual do comando dh
OVERRIDE TARGETS
A debian/rules file using dh can override the command that is run at
any step in a sequence, by defining an override target.
To override dh_command, add a target named override_dh_command to the
rules file. When it would normally run dh_command, dh will instead call
that target. The override target can then run the command with
additional options, or run entirely different commands instead. See
examples below. (Note that to use this feature, you should Build-
Depend on debhelper 7.0.50 or above.)
Override targets can also be defined to run only when building
architecture dependent or architecture independent packages. Use
targets with names like override_dh_command-arch and
override_dh_command-indep. (Note that to use this feature, you should
Build-Depend on debhelper 8.9.7 or above.)
Com relação ao bit da Política ... Um build-indep
target está sendo chamado, mas não sua build-indep
target.