Add support for signature in getPackageArchiveInfo

GET_SIGNATURES was indicated as supported, but it never actually did
anything.

This is needed for the package verifier development sample.

Change-Id: I09ca6790cd8bf9435aa208c0711359b4d76fb278

core/java/android/content/pm/PackageManager.java

@@ -2124,6 +2124,9 @@ public abstract class PackageManager {
         if (pkg == null) {
             return null;
         }
+        if ((flags & GET_SIGNATURES) != 0) {
+            packageParser.collectCertificates(pkg, 0);
+        }
         return PackageParser.generatePackageInfo(pkg, null, flags, 0, 0);
     }