Hey Alan,
I have definitely gotten multiple SDKs into a single build before, but it was quite some time ago.
The flashsdk includes different rake targets for flex3 and flex4, so it should be easy to compile against different top level versions at that point.
If you want to compile against different minor revisions in the same rakefile, you'll have to get more creative.
I believe the SDKs are generally backwards compatible, so you should be able to load the most recent flashsdk gem, but then in any given task, you'll want to set the 'executable' to a path on disk (relative is probably good) where you've manually downloaded and unpacked the sdk version.
This might look something like:
mxmlc 'bin/SomeProject-4.4.swf' do |t|
t.executable = 'sdks/4.4.x./bin/mxmlc'
t.input = 'src/SomeProject.as'
end
mxmlc 'bin/SomeProject-4.6.swf' do |t|
t.executable = 'sdks/4.6.x./bin/mxmlc'
t.input = 'src/SomeProject.as'
end
I believe that'll work - please let me know if it doesn't.
Thanks,
Luke