Set is_stubs_module for stubs modules

This change sets is_stubs_module property to true for combined modules
genreated in `combined_apis` and non-updatable stub modules, which are
not generated via java_sdk_library but are maintained separately.

Test: m nothing --no-skip-soong-tests
Bug: 310504781
Merged-In: I1293208e575a76db2cc4dc6c8564369804bb4ac5
Change-Id: I1293208e575a76db2cc4dc6c8564369804bb4ac5
diff --git a/api/StubLibraries.bp b/api/StubLibraries.bp
index 852abdf..2edbd91 100644
--- a/api/StubLibraries.bp
+++ b/api/StubLibraries.bp
@@ -225,6 +225,7 @@
     java_version: "1.8",
     compile_dex: true,
     visibility: ["//visibility:public"],
+    is_stubs_module: true,
 }
 
 java_defaults {
@@ -233,6 +234,7 @@
     system_modules: "none",
     java_version: "1.8",
     compile_dex: true,
+    is_stubs_module: true,
 }
 
 java_defaults {
@@ -716,6 +718,7 @@
         // with its own package-private android.annotation.Nullable.
         "private-stub-annotations-jar",
     ],
+    is_stubs_module: true,
 }
 
 java_genrule {
@@ -770,6 +773,7 @@
         // annotations found, thus should exist inside android.jar.
         "private-stub-annotations-jar",
     ],
+    is_stubs_module: true,
 }
 
 // Listing of API domains contribution and dependencies per API surfaces