Install gcc-arm-linux-gnueabihf and binutils-arm-linux-gnueabihf for arm builds requiring C packages

[Lindenk]

Although it isn't the highest priority, building an arm package using C bindings takes several extra minutes because gcc-arm-linux-gnueabihf and binutils-arm-linux-gnueabihfneed to be installed first.

The fix would be to add gcc-arm-linux-gnueabihf and binutils-arm-linux-gnueabihf to the list of installed packages for the image.

[sfackler]

These are based off of the buildpack-deps image. You should file this request there if you think it should be included in standard official Docker images.