--build should be set to %{_host_alias} (i586-alt-linux) instead of %{_target_platform}. We are building everything on THIS machine, for which _target_platform was set at rpm's build time, so now it's _host_alias. _target_platform depends on --target argument to rpmbuild and can even be set to ``noarch-alt-linux''...
$ rpm --showrc |fgrep _alias -14: _build_alias %{_host_alias} -14: _host_alias i586-alt-linux%{nil} -14: _target_alias %{_host_alias} Maybe we should change _target_alias and use these macros instead?
tracked at https://bugs.launchpad.net/rpm/+bug/911026