Grant CompOS APEX access to OdsignInfo.

We will re-use this format to store the digests of CompOS-generated
artifacts.

Bug: 209572241
Test: Builds
Change-Id: I820015580edfc465c9f03d27613a0cf8e9456bc6
diff --git a/ondevice-signing/proto/Android.bp b/ondevice-signing/proto/Android.bp
index 4b8921e..173aae4 100644
--- a/ondevice-signing/proto/Android.bp
+++ b/ondevice-signing/proto/Android.bp
@@ -26,6 +26,10 @@
         type: "lite",
     },
     srcs: ["odsign_info.proto"],
+    apex_available: [
+        "//apex_available:platform",
+        "com.android.compos",
+    ],
 }
 
 cc_library_static {