Add dependencies on all the makefiles.

This should help prevent broken builds next time I'm messing with
assembler/compiler/linker flags...

Change-Id: I30f15a3ce3c3f3c60cad7bc59aaba9f42d792224
diff --git a/libstdc++/Android.mk b/libstdc++/Android.mk
index 7d27aa8..41e6c4d 100644
--- a/libstdc++/Android.mk
+++ b/libstdc++/Android.mk
@@ -19,6 +19,7 @@
 	src/typeinfo.cpp
 
 LOCAL_MODULE:= libstdc++
+LOCAL_ADDITIONAL_DEPENDENCIES := $(LOCAL_PATH)/Android.mk
 
 LOCAL_CFLAGS := $(libstdc++_cflags)
 
@@ -37,6 +38,7 @@
 LOCAL_CFLAGS := $(libstdc++_cflags)
 
 LOCAL_MODULE:= libstdc++
+LOCAL_ADDITIONAL_DEPENDENCIES := $(LOCAL_PATH)/Android.mk
 
 LOCAL_SYSTEM_SHARED_LIBRARIES := libc