Turning off universal package building

I am running into an issue that I do not understand.  I am trying to
install GEOquery from source using a relatively recent R development
version (2011-12-06).  GEOquery depends on the XML package.  XML installs
fine for i386 on my Mac Pro laptop, but not for the other two architectures
(we can ignore the details of why for now).  When I try to install
GEOquery, this is what I see:

$ R --arch=i386 CMD INSTALL GEOquery.tar.gz
* installing to library
?/Library/Frameworks/R.framework/Versions/2.15/Resources/library?
* installing *source* package ?GEOquery? ...
** R
** inst
** preparing package for lazy loading
** help
*** installing help indices
** building package indices ...
*** tangling vignette sources ...
  ?GEOquery.Rnw?
** testing if installed package can be loaded
*** arch - i386
Setting options('download.file.method.GEOquery'='curl')
*** arch - ppc
Error in paste0("(^|[^%])(%%)*%", spec) : not a BUILTIN function
Calls: Sys.setenv -> .expand_R_libs_env_var -> expand -> gsub -> paste0
Execution halted
*** arch - x86_64
Error : .onLoad failed in loadNamespace() for 'XML', details:
 call: library.dynam("XML", pkgname, libname)
 error: shared object ?XML.so? not found
Error: loading failed
Execution halted
ERROR: loading failed for ?ppc?, ?x86_64?
* removing
?/Library/Frameworks/R.framework/Versions/2.15/Resources/library/GEOquery?
* restoring previous
?/Library/Frameworks/R.framework/Versions/2.15/Resources/library/GEOquery?

Why is R trying to install all three architectures when I have asked for
only i386?  So, how can I install for i386 only?  I'm sure the answer is
well-documented somewhere, but I have not yet found it.

Thanks,
Sean

sessionInfo()

R Under development (unstable) (2011-12-06 r57839)
Platform: i386-apple-darwin9.8.0/i386 (32-bit)

locale:
[1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base

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