* They didn't work before, because the location of the tests caused the
'sysroot' option to crate lookup to be wrong for finding the correct stage's
core/std libraries. This moves the compiled tests from the $host/test
directory into a $host/$stage/test directory. This means that the sysroot will
be correct and the core/std libraries can actually be found
* The LLVM bindings apparently aren't threadsafe, so we can't run multiple tests
in parallel.
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