Add bootclasspath_fragment.

Note that the contents of the bootclasspath_fragment are added as
dependencies to an apex, so there is no need to duplicate them in
java_libs.

Bug: 180105615
Test: atest CtsClasspathsTestCases
Change-Id: Idba141b6dba3c79768c63a0f16b7c584f8d71a9a
Merged-In: Idba141b6dba3c79768c63a0f16b7c584f8d71a9a
diff --git a/Android.bp b/Android.bp
index 4ce6646..d694623 100644
--- a/Android.bp
+++ b/Android.bp
@@ -20,11 +20,11 @@
 apex {
     name: "com.android.sdkext",
     defaults: [ "com.android.sdkext-defaults" ],
+    bootclasspath_fragments: ["com.android.sdkext-bootclasspath-fragment"],
     binaries: [
         "derive_classpath",
         "derive_sdk",
     ],
-    java_libs: [ "framework-sdkextensions" ],
     prebuilts: [
         "cur_sdkinfo",
         "extensions_db",
@@ -60,3 +60,10 @@
     name: "sdkextensions-sdk",
     java_sdk_libs: ["framework-sdkextensions"],
 }
+
+// Encapsulate the contributions made by the com.android.sdkext to the bootclasspath.
+bootclasspath_fragment {
+    name: "com.android.sdkext-bootclasspath-fragment",
+    contents: ["framework-sdkextensions"],
+    apex_available: ["com.android.sdkext"],
+}