[R] source-only package, but still: Error: package 'simple' was built for powerpc-apple-darwin7.9.0

[Paul Shannon]

I have a number simple R functions written for the biologists I work
with.  These functions will evolve, and the documentation will get
steadily better.  I hope to put them in a package on a local
webserver, along with lots of help files, so that the users can easily
update their installation.

The functions are pure R, with no compiled code, but alias, I cannot figure out
how to build this package so that it is portable across operating
systems.

It looks like 'R CMD build' inserts the following line into the resulting package:

     Built: R 2.1.0; powerpc-apple-darwin7.9.0; 2005-05-18 14:28:36; unix

making it impossible for me to later load the package into R running under another OS.
I see this error when I execute  library ('simple') under linux:

   Error: package 'simple' was built for powerpc-apple-darwin7.9.0

I'll be grateful if anyone can help me work around this restriction  ... or
let me know how I am misconstruing the evidence.

Thank you!

 - Paul Shannon
   Institute for Systems Biology
   Seattle