Building Busybox with Android-NDK results for me in a not completely working "mount" applet.
Without SELInux:
busybox.custom.ndk.config
With SELinux:
busybox.custom.selinux.ndk.config
Note:
cust_libs and cust_includes are only necessary for NDK Build
Just for Information. Executing "make clean" will remove the libs inside "cust_libs".
So you have to copy them there again.
Building Busybox with a native ARM-Machine like my Cubietruck results in a normal working "mount" applet.
And it looks like the resuting Busybox is usable for Android.
Without SELInux:
busybox.custom.cubie.config
With SELinux:
busybox.custom.selinux.cubie.config