stubs inheriting from framework-module-stubs-defaults-* now works

This change fixes a problem that droidstub modules inheriting from
framework-module-stubs-defaults-* don't emit any source code. The
problem was happening because

1) --show-annotation was with incorrect format; it had trailing
"," in the parameter list and
2) the class SystemApi was not available to metalava, which made
prevented it from processing any API annotated with @SystemApi.

Fixing the problem by forcibly adding framework annotations to the
sources of the default modules.

Bug: 1241127
Test: `m ike-stubs` and check its output
Change-Id: Icbbbddb4fb68055f27aa314983a9c556e51f037a

apex/Android.bp

@@ -31,12 +31,12 @@ mainline_stubs_args += "--hide-package com.android.server "
 
 priv_apps = " " +
     "--show-annotation android.annotation.SystemApi\\(" +
-        "client=android.annotation.SystemApi.Client.PRIVILEGED_APPS," +
+        "client=android.annotation.SystemApi.Client.PRIVILEGED_APPS" +
     "\\) "
 
 module_libs = " " +
     " --show-annotation android.annotation.SystemApi\\(" +
-        "client=android.annotation.SystemApi.Client.MODULE_LIBRARIES," +
+        "client=android.annotation.SystemApi.Client.MODULE_LIBRARIES" +
     "\\) "
 
 stubs_defaults {
@@ -48,6 +48,7 @@ stubs_defaults {
 stubs_defaults {
     name: "framework-module-stubs-defaults-systemapi",
     args: mainline_stubs_args + priv_apps,
+    srcs: [":framework-annotations"],
     installable: false,
 }
 
@@ -59,11 +60,13 @@ stubs_defaults {
 stubs_defaults {
     name: "framework-module-api-defaults-module_libs_api",
     args: mainline_stubs_args + module_libs,
+    srcs: [":framework-annotations"],
     installable: false,
 }
 
 stubs_defaults {
     name: "framework-module-stubs-defaults-module_libs_api",
     args: mainline_stubs_args + module_libs + priv_apps,
+    srcs: [":framework-annotations"],
     installable: false,
 }