* Ferenc Wagner <wferi@niif.hu>, 2015-07-29, 12:04:
https://www.debian.org/doc/debian-policy/ch-source.html#s-debianrules first says yes, by starting a paragraph as:build-arch (required), build-indep (required)
Yes, they were made mandatory in version 3.9.4 in August 2012. See bugs #374029 and #629385.
but a couple of paragraphs later is also says: Both binary-* targets should depend on the build target, or on the appropriate build-arch or build-indep target, *if provided*, [...]
I filed #793999 to fix this sentence. -- Jakub Wilk