I have set up a daily CI on Github Actions that checks out latest trunk of three Swift packages- swift-argument-parser, swift-crypto, and swift-nio- and cross-compiles them with Swift 5.4 and my Android SDKs for Android AArch64 and x86_64, then runs the x86_64 tests on the Android x86_64 emulator. All tests pass for the first two but swift-nio has some failing tests, which I don't see on AArch64 when I natively build on there, so I disabled that for now and will look into it. Anyone interested in cross-compiling for Android or setting up their own Android CI could use that as a starting point.
Any suggestions for other Swift packages to add to the daily CI are welcome, I think I'll add swift-system and swift-collections next.
I plan to set up a daily CI for the 5.5 branch and trunk too, which will cross-compile the Android SDKs too from the latest source snapshots then use them to cross-compile these Swift packages.
I'll see if I can fix the Android armv7 SDK next, which has an issue with the Swift 5.4 compiler optimizing the stdlib incorrectly.