(either change #3, change #4, or change #5; change #0 was done, but
was an incomplete workaround)
* better package arch filtering for -N , -p (#576990)
-* Convert warning about unknown command-line options back to an error.
* Support DEB_BUILD_OPTIONS=debug ; maybe also support passing
-g -O2 by default. See patch (and discussion of why this breaks
compatability) in #544844.