Specify is_stubs_module property in selected aconfig library modules

"fake_device_config" and "strict_mode_stub" provide stubs and do not
contain any implementation details. Specifying the property
"is_stubs_module" to these modules allow inter-container dependency on
these modules.

Test: m nothing
Bug: 354029496
Change-Id: Ia65ad36ca02c0594fc753935f9cc7c0af6caa20d
diff --git a/tools/aconfig/fake_device_config/Android.bp b/tools/aconfig/fake_device_config/Android.bp
index d6a1f22..7704742 100644
--- a/tools/aconfig/fake_device_config/Android.bp
+++ b/tools/aconfig/fake_device_config/Android.bp
@@ -22,6 +22,7 @@
     sdk_version: "none",
     system_modules: "core-all-system-modules",
     host_supported: true,
+    is_stubs_module: true,
 }
 
 java_library {
@@ -31,4 +32,5 @@
     ],
     sdk_version: "core_current",
     host_supported: true,
+    is_stubs_module: true,
 }