Remove android/arm from 1.4/cross since it's nontrivial to get the -marm compiler backend for it

I think we can safely revisit this later.  I'm really keen on getting this working, since it's awesome, but getting over that compiler hump is going to be fun.

For the curious, I was playing with variations on the following to get this to work:
```Dockerfile
RUN echo 'deb http://http.debian.net/debian sid main' > /etc/apt/sources.list.d/sid.list \
    && dpkg --add-architecture armel \
    && apt-get update && apt-get install -y gcc-arm-linux-gnueabi \
    && rm -rf /var/lib/apt/lists/* \
    && rm /etc/apt/sources.list.d/sid.list
```
(see also https://packages.debian.org/sid/gcc-arm-linux-gnueabi)