Error with 'port -vst install'

[Pieter van Oostrum]

I'm preparing an upgrade for a port that I maintain (fricas). I have made a private upgrade in a local directory, and the normal install succeeds. However, in preparation of th Pull Request I tried 'sudo port -vst install' and this fails with a permission error in the extraction phase.

```
Executing:  cd "/opt/local/var/macports/build/_Users_pieter_Projects_MACPORTS_math_fricas/fricas/work" && /usr/bin/bzip2 -dc '/opt/local/var/macports/distfiles/fricas/fricas-1.3.8-full.tar.bz2' | /usr/bin/tar -xf - 
sip_copy_proc: mkdir(/opt/local/var/macports/sip-workaround/502/usr): Permission denied
Command failed:  cd "/opt/local/var/macports/build/_Users_pieter_Projects_MACPORTS_math_fricas/fricas/work" && /usr/bin/bzip2 -dc '/opt/local/var/macports/distfiles/fricas/fricas-1.3.8-full.tar.bz2' | /usr/bin/tar -xf - 
Exit code: 128
```

It fails to create the directory '/opt/local/var/macports/sip-workaround/502/usr'. In fact on a previous run it failed to create '/opt/local/var/macports/sip-workaround/502' and then I created that directory manually. And then it fails at the next level. I don't like to create the whole directory structure manually. Is there anything else I can do, or is this actually a bug?
-- 
Pieter van Oostrum <pieter at vanoostrum.org>
www: http://pieter.vanoostrum.org/
PGP key: [8DAE142BE17999C4]