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cc374d8056
Summary: Currently, OpenMP handles the `omp requires` clause by emitting a global constructor into the runtime for every translation unit that requires it. However, this is not a great solution because it prevents us from having a defined order in which the runtime is accessed and used. This patch changes the approach to no longer use global constructors, but to instead group the flag with the other offloading entires that we already handle. This has the effect of still registering each flag per requires TU, but now we have a single constructor that handles everything. This function removes support for the old `__tgt_register_requires` and replaces it with a warning message. We just had a recent release, and the OpenMP policy for the past four releases since we switched to LLVM is that we do not provide strict backwards compatibility between major LLVM releases now that the library is versioned. This means that a user will need to recompile if they have an old binary that relied on `register_requires` having the old behavior. It is important that we actively deprecate this, as otherwise it would not solve the problem of having no defined init and shutdown order for `libomptarget`. The problem of `libomptarget` not having a define init and shutdown order cascades into a lot of other issues so I have a strong incentive to be rid of it. It is worth noting that the current `__tgt_offload_entry` only has space for a 32-bit integer here. I am planning to overhaul these at some point as well.