Switch rsg-generator to use no STL, since it is pure C.

We should really fix rsg-generator to install itself, and then be invoked
from a location with access to libc++.so, but this fixes things for the
time being.

Change-Id: Icbcd4e626e76f17cb32ca3631ef40172ee15910e
diff --git a/Android.mk b/Android.mk
index 4d76839..cb3ef33 100644
--- a/Android.mk
+++ b/Android.mk
@@ -82,6 +82,8 @@
     spec.l \
     rsg_generator.c
 
+LOCAL_CXX_STL := none
+
 include $(BUILD_HOST_EXECUTABLE)
 
 # TODO: This should go into build/core/config.mk