[4.0.x] waf doesn't seem to be honoring --build-number=$BUILD_NUMBER

[David Nalley]

I am running ./waf rpm --package-version=4.0.1 --build-number=2  from
within the 4.0.1 release tarball and --build-number doesn't seem to be
honored. I have a workaround, but anyone have insight into why waf
isn't passing this to %{_rel}??

--David