Summary:
This adds a basic outline for adding 'conformance' tests. These are
tests that are intended to check device code against a standard. In this
case, we will expect this to be filled with math conformance tests to
make sure their results are within the ULP requirements we demand.
Right now this just *assumes* the GPU libc is there, meaning you'll
likely need to do a manual `ninja` before doing `ninja -C
runtimes/runtimes-bins offload.conformance`.
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