Don't build libc++ libs for ub branches

Change-Id: Ib73f6d38ed7d2bcb759a0f3e4ee44010b552fddc
diff --git a/src/Android.mk b/src/Android.mk
index e7f8ff7..e257d42 100644
--- a/src/Android.mk
+++ b/src/Android.mk
@@ -97,6 +97,8 @@
 
 include $(BUILD_STATIC_LIBRARY)
 
+# Don't build for unbundled branches
+ifeq (,$(TARGET_BUILD_APPS))
 #######################################################################
 # libc++
 
@@ -155,3 +157,4 @@
 
 include external/libcxx/libcxx.mk
 include $(BUILD_STATIC_LIBRARY)
+endif