How to add AAR to classpath?

I have an AAR for an SDK (Azure speech services) that I have placed in the Assets/Plugins/Android folder. The AAR file is marked in Unity for inclusion in the Android build.

I have a source file also in the same directory. According to the 2018.2 documentation, this should build the file as a plugin using the Gradle build.

Indeed, I’m getting that file being compiled, but it doesn’t seem to have access to the classes in the AAR. I’m getting a bunch of errors like:

CommandInvokationFailure: Gradle build failed. 
C:\Program Files\Java\jdk1.8.0_181\bin\java.exe -classpath "C:\Unity\2018.2.10f1\Editor\Data\PlaybackEngines\AndroidPlayer\Tools\gradle\lib\gradle-launcher-4.2.1.jar" org.gradle.launcher.GradleMain "-Dorg.gradle.jvmargs=-Xmx2048m" "assembleRelease"

C:\Temp\AndroidSpeechTest\Temp\gradleOut\src\main\java\ error: cannot find symbol
            final SpeechRecognizer reco = new SpeechRecognizer(speechConfig, audioInput);

How do I add the AAR file to the classpath for compiling this Java source file?

My error here. The Java code had other errors that made me think the AAR was not on the classpath. Unity correctly added the library to the Gradle dependencies.

If someone else runs into something like this, export the project and load into Android Studio. This will give you better support for debugging missing imports and such.