Hi Rich,
1. Which flavor of tiny core: I understand that there is no obligation to compile for one and not the other. My thoughts where let's compile for all TC supported architectures. This will achieve conformity across TC users, making a TC user experience better across architectures, which is done through cross compilation. My main reason for this comment is is to see that TC is not a separate OS among the different architectures (one can jump from Aarch-32 to x86-32 without being a lost within each other). My hope is that every architecture is treated the same, although when cross compiling have notice some deference's.
Your question in regards to "I'm not aware of any cross compilation packages in TC" my have been misinterpreted. Let me explain while compiling a program one can compile for different architectures while compiling. Lets say where compiling for Aarch-64 and made our configurations, it is then easy to change our configurations for example to compile for x86-32 with the right libraries (hence leading back to the above). The logic behind this is once the submitter of the extension/program has accumulated the knowledge of the program/extension why not distribute among the supported platforms for a better TC experience (if all TC are equal).
In reply "When I've submitted extensions, I've supplied a source package that includes a build script". I totally agree with supplying a build file this way an understanding is formed for the submission. I also understand that one does not have all the hardware so some assumptions have to be made before submitting so cross compilation and fingers crosses. :-)