Allow Android Java shim to be built as an AAR

android-project/app/build.gradle

@@ -1,10 +1,19 @@
+def buildAsLibrary = project.hasProperty('BUILD_AS_LIBRARY');
+def buildAsApplication = !buildAsLibrary
+if (buildAsApplication) {
     apply plugin: 'com.android.application'
+}
+else {
+    apply plugin: 'com.android.library'
+}
 
 android {
     compileSdkVersion 16
     buildToolsVersion "26.0.1"
     defaultConfig {
+        if (buildAsApplication) {
             applicationId "org.libsdl.app"
+        }
         minSdkVersion 14
         targetSdkVersion 16
         versionCode 1
@@ -22,6 +31,7 @@ android {
             proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
         }
     }
+    if (!project.hasProperty('EXCLUDE_NATIVE_LIBS')) {
         sourceSets.main {
             jniLibs.srcDir 'libs'
         }
@@ -30,9 +40,23 @@ android {
                 path 'jni/Android.mk'
             }
         }
+       
+    }
     lintOptions {
         abortOnError false
     }
+    
+    if (buildAsLibrary) {
+        libraryVariants.all { variant ->
+            variant.outputs.each { output ->
+                def outputFile = output.outputFile
+                if (outputFile != null && outputFile.name.endsWith(".aar")) {
+                    def fileName = "org.libsdl.app.aar";
+                    output.outputFile = new File(outputFile.parent, fileName);
+                }
+            }
+        }
+    }
 }
 
 dependencies {