Description

Mishal recently asked the Android workgroup to submit a Dockerfile which builds an Android SDK for the 6.2 and trunk branches, so @marcprux and I will be putting one together in the coming weeks. Here's a checklist of the decisions that have to be made:

• What Android API should the Swift runtime be built against? We've tentatively decided on API 28, as that is when most of the posix_spawn APIs were added to the Bionic libc, which some parts of Foundation depend on.
• Do we bundle the Android C/C++ sysroot from the NDK with the Swift SDK? Probably safest not to, which means we'll have to try out the existing SDK bundle support for using an external C/C++ sysroot now.
• Do we support FoundationXML and FoundationNetworking, which will require cross-compiling their libxml2, libcurl, and BoringSSL dependencies also? We plan to look into cross-compiling all those libraries from source for Android.
• The new Testing library and a few other toolchain product repos have shifted to using CMake Toolchain files when configuring their build for linux and mac. We need to investigate doing the same for Android.
• Testing calls the backtrace() API, which wasn't added to Bionic till API 33. Investigate if that can be disabled for now, or if we want to add a backport library.

Additional information

Much of this already works in build-script and the corelibs, but a few tweaks will be needed.