be defined (in /etc/make.conf, say) and set to the additional architectures
that need to be compiled in. So on alpha I set CROSS_TOOLS = i386.
On i386 you can't build alpha due to lack of 64-bit support on 32-bit
architectures, but that's a GNU problem.
This change relies on makefiles in the binutils sub-directories having
the extension defined in the CROSS_TOOLS, instead of those makefiles
being selected based on the host architecture.
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