Only generated notices for built variants.

Test: banchan dcla-notice mainline_modules_arm64; m apps_only dist
Change-Id: I6b0e2eb64f2f3db87dfed68affb44fe141da3eaa

android/gen_notice.go

@@ -61,6 +61,9 @@ func (s *genNoticeBuildRules) GenerateBuildActions(ctx SingletonContext) {
 				if mod == nil {
 					continue
 				}
+				if !mod.Enabled() { // don't depend on variants without build rules
+					continue
+				}
 				modules = append(modules, mod)
 			}
 		}