msp430-binutils forces linking

[tpetry]

for building msp430-gcc you are forced to link msp430-binutils but this is a problem if you already have binutils installed.
It would be much better if msp430-binutils would be keg_only.

[tpetry]

keg_only would be stupid, because the bin-executables would not be found. But no executable of msp430-binutils conflicts with binutils so it would be nice if it could be linked directly. At the moment you have to use force the linking (which would overwrite duplicate files).

[sampsyo]

Yes, forcing the linking is unfortunate! I couldn't find a way around it, though, to install both packages under the same prefix. If someone better with the Homebrew API is watching, I'd love to remove that step.