feat(tests): Apple Silicon Support

anki-android-backend-testing contains pre-compiled Rust code so
Robolectric can load it and run natively.

We can't currently include an Apple Silicon (AS) dylib inside
anki-android-backend-testing (`cross` doesn't compile AS code yet)

But, we can compile an AS dylib on an AS Mac and reference it.

So we include the dylib in the releases folder of Anki-Android-Backend
and add functionality to specify an environment variable to load this
dylib from disk, instead of from the .jar

Instructions (for 0.1.10):

Download librsdroid-arm64.dylib from https://github.com/ankidroid/Anki-Android-Backend/releases/tag/0.1.10

And add the following environment variables:
one to the path and one for the version

```
export ANKIDROID_BACKEND_PATH="/Users/davidallison/StudioProjects/Anki-Android-Backend/rslib-bridge/target/aarch64-apple-darwin/release/librsdroid-arm64.dylib"
export ANKIDROID_BACKEND_VERSION="0.1.10"
```

Library generated from:
```
davidallison@Davids-MBP rslib-bridge % pwd
/Users/davidallison/StudioProjects/Anki-Android-Backend/rslib-bridge
cross build --release --features no-android --verbose --target aarch64-apple
```
on an AS MacBook

Fixes ankidroid/Anki-Android-Backend#164

AnkiDroid/build.gradle

@@ -77,7 +77,7 @@ android {
             // Check Crash Reports page on developer wiki for info on ACRA testing
             buildConfigField "String", "ACRA_URL", '"https://ankidroid.org/acra/report"'
 //            buildConfigField "String", "ACRA_URL", '"https://918f7f55-f238-436c-b34f-c8b5f1331fe5-bluemix.cloudant.com/acra-ankidroid/_design/acra-storage/_update/report"'
-
+            buildConfigField "String", "BACKEND_VERSION", "\"$ankidroid_backend_version\""
             // #6009 Allow optional disabling of JaCoCo for general build (assembleDebug).
             // jacocoDebug task was slow, hung, and wasn't required unless I wanted coverage
             if (project.rootProject.file('local.properties').exists()) {
@@ -102,6 +102,7 @@ android {
             proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
             signingConfig signingConfigs.release
             buildConfigField "String", "ACRA_URL", '"https://ankidroid.org/acra/report"'
+            buildConfigField "String", "BACKEND_VERSION", "\"$ankidroid_backend_version\""
             resValue 'color', 'anki_foreground_icon_color_0', "#FF29B6F6"
             resValue 'color', 'anki_foreground_icon_color_1', "#FF0288D1"
         }
@@ -302,18 +303,15 @@ dependencies {
     implementation 'com.fasterxml.jackson.core:jackson-databind:2.13.2'
     implementation 'com.github.CanHub:Android-Image-Cropper:3.1.3'
 
-
-    // == Rust conversion (from Anki-Android-Backend on GitHub) ==
-    String backendVersion = "0.1.10" // We want both testing and implementation on the same version
     // build with ./gradlew rsdroid:assembleRelease
-    // In my experience, using `files()` currently requires a reindex operation, which is slow.
+    // In my experience, using `files()` currently requires a reindex operation.
     // implementation files("C:\\GitHub\\Rust-Test\\rsdroid\\build\\outputs\\aar\\rsdroid-release.aar")
     implementation 'com.google.protobuf:protobuf-java:3.19.4' // This is required when loading from a file
-    implementation "io.github.david-allison-1:anki-android-backend:$backendVersion"
+    implementation "io.github.david-allison-1:anki-android-backend:$ankidroid_backend_version"
     // build with ./gradlew rsdroid-testing:assembleRelease
     // RobolectricTest.java: replace RustBackendLoader.init(); with RustBackendLoader.loadRsdroid(path);
     // A path for a testing library is typically under rsdroid-testing/assets
-    testImplementation "io.github.david-allison-1:anki-android-backend-testing:$backendVersion"
+    testImplementation "io.github.david-allison-1:anki-android-backend-testing:$ankidroid_backend_version"
 
     // May need a resolution strategy for support libs to our versions
     implementation "ch.acra:acra-http:$acra_version"

AnkiDroid/src/test/java/com/ichi2/anki/RobolectricTest.kt

@@ -89,7 +89,24 @@ open class RobolectricTest : CollectionGetter {
             runTasksInBackground()
         }
 
-        RustBackendLoader.init()
+        // Allow an override for the testing library (allowing Robolectric to access the Rust backend)
+        // This allows M1 macs to access a .dylib built for arm64, despite it not existing in the .jar
+        val backendPath = System.getenv("ANKIDROID_BACKEND_PATH")
+        if (backendPath != null) {
+            if (BuildConfig.BACKEND_VERSION != System.getenv("ANKIDROID_BACKEND_VERSION")) {
+                throw java.lang.IllegalStateException(
+                    "AnkiDroid backend testing library requires an update.\n" +
+                        "Please update the library at '$backendPath' from https://github.com/ankidroid/Anki-Android-Backend/releases/ (v ${System.getenv("ANKIDROID_BACKEND_VERSION")})\n" +
+                        "And then set \$ANKIDROID_BACKEND_VERSION to ${BuildConfig.BACKEND_VERSION}\n" +
+                        "Error: \$ANKIDROID_BACKEND_VERSION: expected '${BuildConfig.BACKEND_VERSION}', got '${System.getenv("ANKIDROID_BACKEND_VERSION")}'"
+                )
+            }
+            // we're the right version, load the library from $ANKIDROID_BACKEND_PATH
+            RustBackendLoader.loadRsdroid(backendPath)
+        } else {
+            // default (no env variable): Extract the backend testing lib from the jar
+            RustBackendLoader.init()
+        }
 
         // If you want to see the Android logging (from Timber), you need to set it up here
         ShadowLog.stream = System.out

build.gradle

@@ -7,6 +7,7 @@ buildscript {
     ext.kotlin_version = '1.6.10'
     ext.lint_version = '30.1.2'
     ext.acra_version = '5.7.0'
+    ext.ankidroid_backend_version = '0.1.10'
 
     repositories {
         google()