Fix order of soinfo links (repairs libcxx tests).

(cherry picked from commit b2a30ee8d209154efc367db11b4167a5d6db605f)

Change-Id: I59c5333bc050cbbea14051cea9220be2f64ee383
diff --git a/tests/Android.mk b/tests/Android.mk
index 64d3b59..69ff811 100644
--- a/tests/Android.mk
+++ b/tests/Android.mk
@@ -257,6 +257,7 @@
     -Wl,-u,DlSymTestFunction \
 
 bionic-unit-tests_c_includes := \
+    bionic/libc \
     $(call include-path-for, libpagemap) \
 
 bionic-unit-tests_shared_libraries_target := \