Add "updatable" property to ApexModule interface.

For a given variant of a module that implements ApexModule interface,
the "updatable" property tests if this variant comes from an updatable
apex. For platform variants it is always false.

Test: lunch aosp_walleye-userdebug && m nothing
Bug: 138994281
Change-Id: I2d4c54fb397e29dc9b3203be7fb17be4536529f7
diff --git a/apex/apex.go b/apex/apex.go
index 8463ac1..1f9e1f3 100644
--- a/apex/apex.go
+++ b/apex/apex.go
@@ -845,6 +845,7 @@
 		apexBundles = []android.ApexInfo{{
 			ApexName:      mctx.ModuleName(),
 			MinSdkVersion: a.minSdkVersion(mctx),
+			Updatable:     proptools.Bool(a.properties.Updatable),
 		}}
 		directDep = true
 	} else if am, ok := mctx.Module().(android.ApexModule); ok {