I figured if you're happy with your current Android SDK, you could just move it to linux and then configure a similar destination.json for SPM in the linux Swift toolchain to use it. I wrote up some info on what the different cross-compilation flags mean a couple months ago and you could look at the android.json I use to cross-compile SPM itself from linux for the Termux Android app (that's specific to the standalone toolchain for Android that Termux uses, but it gives you an idea).