Add -ldl for opannotate, oparchive, etc, in pp/Android.mk

The new libbfd.a is compiled with plugin enabled.  The plugin.o in
it need dlopen, dlsym, etc

Change-Id: I63912ddc151fe3f6a34274e6200db6e7a16c910d
diff --git a/pp/Android.mk b/pp/Android.mk
index b5d2e0a..fa1cf6e 100644
--- a/pp/Android.mk
+++ b/pp/Android.mk
@@ -31,7 +31,7 @@
 	libiberty \
 	libintl
 
-common_ldlibs := -lz $(common_host_ldlibs_libiconv)
+common_ldlibs := -lz $(common_host_ldlibs_libiconv) -ldl
 
 ifeq ($(HAVE_LIBBFD),true)