Fix iOS build, and add iOS step to CI (#4898)

<!--
Please read the "Making a PR" section of
[`CONTRIBUTING.md`](https://github.com/emilk/egui/blob/master/CONTRIBUTING.md)
before opening a Pull Request!

* Keep your PR:s small and focused.
* The PR title is what ends up in the changelog, so make it descriptive!
* If applicable, add a screenshot or gif.
* If it is a non-trivial addition, consider adding a demo for it to
`egui_demo_lib`, or a new example.
* Do NOT open PR:s from your `master` branch, as that makes it hard for
maintainers to test and add commits to your PR.
* Remember to run `cargo fmt` and `cargo clippy`.
* Open the PR as a draft until you have self-reviewed it and run
`./scripts/check.sh`.
* When you have addressed a PR comment, mark it as resolved.

Please be patient! I will review your PR, but my time is limited!
-->

This PR
- adds a pipeline to check the ios build
- removes the iOS WaitUntil workaround, which doesn't seem to be
necessary anymore after the winit update (and caused the build for iOS
to fail again because of a missing self
- ~removes a iOS workaround for window size which doesn't seem necessary
anymore~
Turns out it was still needed (but you need to actually restart the app
for the issue to show up, so I didn't catch it first)
- fixes some cargo check errors in run.rs

I've done all these changes in a single PR because otherwise the
pipeline doesn't run but I can also split them in separate PRs if that
makes it easier to review

.github/workflows/rust.yml

@@ -1,4 +1,4 @@
-on: [push, pull_request]
+on: [ push, pull_request ]
 
 name: Rust
 
@@ -167,6 +167,26 @@ jobs:
 
   # ---------------------------------------------------------------------------
 
+  ios:
+    name: ios
+    runs-on: ubuntu-22.04
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: dtolnay/rust-toolchain@master
+        with:
+          toolchain: 1.76.0
+          targets: aarch64-apple-ios
+
+      - name: Set up cargo cache
+        uses: Swatinem/rust-cache@v2
+
+        # Default features are disabled because glutin doesn't compile for ios.
+      - run: cargo check --features wgpu --target aarch64-apple-ios --no-default-features
+        working-directory: crates/eframe
+
+  # ---------------------------------------------------------------------------
+
   windows:
     name: Check Windows
     runs-on: windows-latest