Doesn't link yet due to "multiple definitions of malloc", because some are supplied by some library of bash itself. Really odd.

I really really wish I could actually test this on redox. All I know is: it compiles

Transmuting from an immutable to a mutable reference is undefined
behavior in Rust, with the exception of UnsafeCell which tells the
optimizer to not draw too many conclusions. Sadly UnsafeCell::get cannot
yet be used in statics (see https://github.com/rust-lang/rust/issues/51718),
so this works around that by making the statics into functions and
making C macros to call those.