Bug#670733: ocaml-cry: FTBFS: Incorrectly thinks it's building as root

[Hendrik Tews <hendrik@askra.de>]

Hi,

I played a bit around to investigate the problem. What I see is:

- inside pbuilder, after installing the build dependencies and
  after patching the sources, dh_clean runs as root
  [env says $SUDO_USER=tews and $USER=root; id says uid=0(root)
  gid=0(root)]

- Later the configure script of the package runs not as root. At
  line 2871 in configure, where the root test is, id says 

    uid=56789(pbuilder) gid=56789(pbuilder) groups=56789(pbuilder)

  however, env still says $SUDO_USER=tews and $USER=root. The
  configure script runs `whoami` only if $USER is empty.
  Therefore configure believes $USER=root and aborts.

For me this looks like pbuilder is not setting the environment
correctly when changing to the non-root user. Or the configure
script is wrong in taken the contents of $USER.

Gruss,

Hendrik

PS. To reproduce
- pbuilder create
- pbuilder login --save-after-login
- in the pbuilder shell: useradd -m -u 56789 pbuilder
- put "BUILDUSERNAME=pbuilder" into /etc/pbuilderrc
- build package with git-buildpackage --git-builder=pdebuild