Skia is not so terrible, you just have to use their slightly obscure build tool. And it produces >8GB build artefacts with ~50 or more dependencies... Come to think of it is a bit of a nightmare.
I tried to use it a few times, but having to configure a Google build environment, without Google class workstations, meant I always gave up in the process and used Skia.Sharp instead.
Thanks for the heads up, but doing it across Windows/UWP, Android and iOS requires a bit more of effort than what you described, hence Skia.Sharp instead.
I'm doing exactly that though. To compile for iOS for example, create a separate output directory with `target_os="ios" target_cpu="arm64"`. You can see a few more examples here https://skia.org/user/build
Unfortunately, C++ libraries are a bit harder to use than other languages, hopefully the modules proposal will make this a lot easier.
Just in case: Skia can be built without Google build environment. For the Sciter (https://sciter.com) I just included all needed files into projects ( MSVC and XCode ). That setup takes some initial time but after that it works as any other library like libpng, etc.