feat: Make updater build on iOS (#22)

Doesn't work yet, but does at least build (and log).

BUILDING_ENGINE.md

@@ -134,3 +134,14 @@ When testing on my machine, I use something like:
 $PATH_TO_ENGINE_SRC="$HOME/Documents/GitHub/engine/src"
 shorebird --local-engine-src-path=$PATH_TO_ENGINE_SRC --local-engine=android_release_arm64 run
 ```
+
+
+# For iOS
+
+```
+rustup target add aarch64-apple-ios x86_64-apple-ios
+```
+
+```
+cargo build --target aarch64-apple-ios --target x86_64-apple-ios --release
+```

library/Cargo.toml

@@ -48,6 +48,11 @@ android_logger = "0.13.0"
 # Send panics to log (instead of stderr), thus logcat on Android.
 log-panics = { version = "2", features = ["with-backtrace"]}
 
+[target.'cfg(target_os = "ios")'.dependencies]
+# Use stderr for logging on iOS.
+simple-logging = "2.0.2"
+# Send panics to syslog (instead of stderr).
+log-panics = { version = "2", features = ["with-backtrace"]}
 
 [dev-dependencies]
 tempdir = "0.3.7"

library/src/config.rs

@@ -220,5 +220,7 @@ pub fn current_platform() -> &'static str {
     static PLATFORM: &str = "windows";
     #[cfg(target_os = "android")]
     static PLATFORM: &str = "android";
+    #[cfg(target_os = "ios")]
+    static PLATFORM: &str = "ios";
     return PLATFORM;
 }

library/src/logging.rs

@@ -11,8 +11,17 @@ pub fn init_logging() {
     debug!("Logging initialized");
 }
 
-#[cfg(not(target_os = "android"))]
+#[cfg(target_os = "ios")]
 pub fn init_logging() {
-    // Nothing to do on non-Android platforms.
-    // Eventually iOS/MacOS may need something here.
+    // I could not figure out how to get fancier logging set up on iOS
+    // but logging to stderr seems to work.
+    use log::LevelFilter;
+    use std::io;
+    simple_logging::log_to(io::stderr(), LevelFilter::Info);
+    debug!("Logging initialized");
+}
+
+#[cfg(all(not(target_os = "android"), not(target_os = "ios")))]
+pub fn init_logging() {
+    // Nothing to do on non-Android, non-iOS platforms.
 }