Handle uname -m returning arm64

docs/_developer_onboarding.md

@@ -132,7 +132,7 @@ Prerequisites:
   ```
 * Install the Android Rust toolchain for your machine's hardware:
   ```
-  rustup target add `uname -m`-linux-android
+  rustup target add aarch64-linux-android x86_64-linux-android
   ```
 * Depending on the location of the Android SDK, you may need to set
   `ANDROID_HOME`:

tools/sdk/build_rust_sdk.sh

@@ -60,6 +60,9 @@ buildApp=${buildApp:-no}
 cd "${elementPwd}"
 
 default_arch="$(uname -m)-linux-android"
+# On ARM MacOS, `uname -m` returns arm64, but the toolchain is called aarch64
+default_arch="${default_arch/arm64/aarch64}"
+
 read -p "Enter the architecture you want to build for (default '$default_arch'): " target_arch
 target_arch="${target_arch:-${default_arch}}"