Buildsys problem

[David Lutterkort <dlutter redhat com>]

I ran into a problem when trying to rebuild ruby-postgres for FC6
(plague job 17228) The build fails during %install on i386 with this:
        Executing(%install): /bin/sh -e /var/tmp/rpm-tmp.65031
        + umask 022
        + cd /builddir/build/BUILD
        + cd ruby-postgres-0.7.1
        + LANG=C
        + export LANG
        + unset DISPLAY
        + rm -rf /var/tmp/ruby-postgres-0.7.1-root-mockbuild
        + make -j2 DESTDIR=/var/tmp/ruby-postgres-0.7.1-root-mockbuild install
        mkdir -p /var/tmp/ruby-postgres-0.7.1-root-mockbuild/usr/lib/ruby/site_ruby/1.8/i386-linux
        /usr/bin/install -c -m 0755 postgres.so /var/tmp/ruby-postgres-0.7.1-root-mockbuild/usr/lib/ruby/site_ruby/1.8/i386-linux
        /usr/bin/install: cannot create regular file `/var/tmp/ruby-postgres-0.7.1-root-mockbuild/usr/lib/ruby/site_ruby/1.8/i386-linux': No such file or directory
        make: *** [/var/tmp/ruby-postgres-0.7.1-root-mockbuild/usr/lib/ruby/site_ruby/1.8/i386-linux/postgres.so] Error 1
        error: Bad exit status from /var/tmp/rpm-tmp.65031 (%install)
        
What has me puzzled is that the build succeeds in plague for x86_64, and
in my own i386 mock buildroot (built from a local rawhide mirror) Any
idea why the mkdir would succeed but the install into that very same
directory fail ?

thanks,
David