[Rd] Support for noarch packages in /usr/share/R/library

[Tom 'spot' Callaway]

As originally raised here:
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=231220

It has been proposed that R should support noarch packages
in /usr/share/R/library in addition to architecture specific packages
in /usr/lib/R/library or /usr/lib64/R/library.

For example, the mAr addon doesn't have any architecture specific bits.
Strictly speaking, the Filesystem Hierarchy Standard says it doesn't
belong in /usr/lib, but rather, /usr/share.

Ideas on the best way to resolve this would be greatly appreciated.

Thanks in advance,

~spot