Fix order of soinfo links (repairs libcxx tests).

Change-Id: Iee9de09657351cd6a7512784ca797e4b84cdd98b
diff --git a/tests/Android.mk b/tests/Android.mk
index cb588d7..49efdad 100644
--- a/tests/Android.mk
+++ b/tests/Android.mk
@@ -264,6 +264,7 @@
     -Wl,-u,DlSymTestFunction \
 
 bionic-unit-tests_c_includes := \
+    bionic/libc \
     $(call include-path-for, libpagemap) \
 
 bionic-unit-tests_shared_libraries_target := \