Bug#905347: sbuild should default to --no-arch-all for cross builds
During the DebConf18 cross bof it was mentioned that cross building with
sbuild is still difficult, because you need to remember so many options.
Until (not so) recently, sbuild defaulted to --no-arch-all. That default
was flipped and now it defaults to full builds -- even for cross
compilation. Satisfying Build-Depends-Indep for cross compilation often
doesn't work -- and isn't necessary. So the usual cross builder wants to
pass --no-arch-all now. I suggest that sbuild flips the default back for
cross compilation only.