Ambiguous build-dependencies

[Ian Jackson <ian@davenant.greenend.org.uk>]

I've been working on getting my automatic package tester working.
It's currently running but I've redirected its automatic bug
submission emails to me, while I make sure that the bugs it reports
are correct.

One common problem that it finds is ambiguously specified
Build-Depends.  For example:

 lenny:~# apt-get build-dep acpi
 Reading package lists... Done
 Building dependency tree       
 Reading state information... Done
 Package automaken is a virtual package provided by:
   automake1.9 1.9.6+nogfdl-3
   automake1.8 1.8.5+nogfdl-2
   automake1.7 1.7.9-9
   automake 1:1.10+nogfdl-1
 You should explicitly select one to install.
 E: Package automaken has no installation candidate
 E: Failed to satisfy Build-Depends dependency for acpi: automaken
 lenny:~#

The buildds use a different algorithm which doesn't choke in this
case, although I don't know how they decide what to use.

Is this a bug in the package(s); or is it a bug in apt ?  After all if
it really doesn't matter which version is installed and the resulting
binaries will be correct, then any version will do.

I think that we ought really to be sure what the build-dependencies
mean, so I think this situation is a bug in the package.  Do other
people agree ?

Ian.