isCompatible concerns itself with architecture compatibility which does
not constitute executability by itself, since there are other key
factors like the Kernel/syscall interface targeted. As mode switching is
considered compatible (e.g. ppc64le and ppc64), we can't even use
isCompatible to establish the architecture subset of executability.
For the lack of a better alternative, we'll just compare the system
tuples for now which will loose us support for x86_64-linux ->
i686-linux, but this is probably a bearable consequence.
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