Add a system server JAR

Add a Java system server classpath fragment to wrap access to
composd. Provide initially empty SystemService and JobService classes.

Bug: 199147668
Test: manual
Change-Id: I5b2bb2f4c9b9086cca85983d0a659ea92409f6bf
diff --git a/compos/aidl/Android.bp b/compos/aidl/Android.bp
index 4d36d3d..7036511 100644
--- a/compos/aidl/Android.bp
+++ b/compos/aidl/Android.bp
@@ -9,6 +9,11 @@
         "com/android/compos/*.aidl",
     ],
     backend: {
+        java: {
+            apex_available: [
+                "com.android.compos",
+            ],
+        },
         rust: {
             enabled: true,
             apex_available: [