ndk-build allow to speed the build speed by using several threads, using the -jX option (where X is the number of core you want to use).
In VLC, it is set to -j1. After trying to change it to -j8, it seems there is a good reason for it : by doing so, weird compilation errors happens (mainly File Truncated, missing file etc ...), which all seem to be related to multi-threading not properly synchronized.
From what I remember, it seems to be caused by the fact that there are several modules in the same Android.mk, something ndk-build doesn't like.
Is modifying that something planned or is fixing that too hard ?
On ndk-r9, there are also warnings due to how external libraries are referenced in Android.mk (WARNING:jni/Android.mk:vlcjni: non-system libraries in linker flags: [...] This is likely to result in incorrect builds. Try using LOCAL_STATIC_LIBRARIES or LOCAL_SHARED_LIBRARIES instead to list the library dependencies of the current module)