Use xbuild instead of cargo apk in the CI

In addition to cargo apk being deprecated, xbuild also has support for
ios.

Signed-off-by: John Nunley <dev@notgull.net>

xbuild-target/Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name = "xbuild-target"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies.winit]
+version = "0.29.1-beta"
+path = ".."
+features = ["android-game-activity"]
+

xbuild-target/README.md

@@ -0,0 +1,4 @@
+# xbuild-target
+
+This is a crate that can be built via `x build` in order to simplify CI testing.
+

xbuild-target/src/main.rs

@@ -0,0 +1,6 @@
+fn main() {
+    winit::event_loop::EventLoop::new()
+        .unwrap()
+        .run(|_, _, _| todo!())
+        .ok();
+}