Vendor dependencies

Let's see how I like this workflow.

vendor/iana-time-zone/src/tz_android.rs

@@ -0,0 +1,27 @@
+use std::sync::Once;
+
+use android_system_properties::AndroidSystemProperties;
+
+use crate::ffi_utils::android_timezone_property_name;
+
+pub(crate) fn get_timezone_inner() -> Result<String, crate::GetTimezoneError> {
+    let key = android_timezone_property_name();
+
+    get_properties()
+        .and_then(|properties| properties.get_from_cstr(key))
+        .ok_or(crate::GetTimezoneError::OsError)
+}
+
+fn get_properties() -> Option<&'static AndroidSystemProperties> {
+    static INITIALIZED: Once = Once::new();
+    static mut PROPERTIES: Option<AndroidSystemProperties> = None;
+
+    INITIALIZED.call_once(|| {
+        let properties = AndroidSystemProperties::new();
+        // SAFETY: `INITIALIZED` is synchronizing. The variable is only assigned to once.
+        unsafe { PROPERTIES = Some(properties) };
+    });
+
+    // SAFETY: `INITIALIZED` is synchronizing. The variable is only assigned to once.
+    unsafe { PROPERTIES.as_ref() }
+}