debian/control: architecture restrictions for builds

[Nico Schlömer <nico.schloemer@gmail.com>]

Hi all,

a quick question about architecture restrictions in `debian/control`.

I have a large tarball which I configure and compile, and then break
up into a number of Debian packages (similar to boost). Unfortunately,
one of the components doesn't compile on 32-bit architectures, which
means that the entire tarball build fails on 32-bit archs.
Now, like I said, `debian/control` lists a number of packages, complete with
```
Package: libmyproject-subpackage-7
Architecture: any
Section: libs
[...]
```
Restricting the architecture to
```
Package: libmyproject-badsubpackage-7
Architecture: amd64
```
only for that one subpackage doesn't cut it. Where do place the
restriction though?

–Nico