Recompiling Rust packages on ppc64

[Simon Richter <sjr@debian.org>]

Hi,

#1110059 has been fixed and rustc generates POWER4 instead of POWER8 code.

1. Can someone verify that the new setting is actually correct? CellBE 
is POWER5 IIRC, so that should be fine with POWER4 code, what about 970?
2. I suppose Rust packages need binNMUs?
3. Do we need to provide guidance to users who have the broken version 
of sqv installed?

   Simon