This was a request to the list. A good idea, if we can ever implement it.
Obviously not a big issue, though.

"
The error message is not particularly meaningful. I suggest
that the build process checks for availability of the
bcmath stuff and indicates where to download this if the
required files are missing.

In fact, I suggest that all configure fragments handle this
as follows:

- if the configuration option requests that a module is
  included, but the config stuff cannot find that module
  under the indicated location and any of the default
  locations,
- configure issues a warning including the URL where the
  missing module can be downloaded.
-- kk@netuse.de"