[OE-core] SDK meta-toolchain

[Kyle Farnsworth]

I'm a bit confused about what exactly meta-toolchain is building?  It
seems to be bitbaking gcc and creating a toolchain with the prefix
x86_64-oesdk-linux- (default SDK_PREFIX) but I'm not sure what it is.  
Is it a cross-compile for my target MACHINE or a compiler for my build
machine?  Based on the prefix name I am assuming the latter.

Thanks for any help.
Kyle