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/composd/aidl/Android.bp b/compos/composd/aidl/Android.bp
index 62c1b40..376313b 100644
--- a/compos/composd/aidl/Android.bp
+++ b/compos/composd/aidl/Android.bp
@@ -9,7 +9,7 @@
     unstable: true,
     backend: {
         java: {
-            apex_available: ["//apex_available:platform"],
+            apex_available: ["com.android.compos"],
         },
         rust: {
             enabled: true,