PR #10638: Handle no-op custom call in the emitter
PR #10638: Handle no-op custom call in the emitter

Imported from GitHub PR https://github.com/openxla/xla/pull/10638

The AllocateBuffer custom call (a.k.a. `kNopCustomCallTarget`) is no-op because the runtime allocates the buffer. Let us handle AllocateBuffer by emitting nothing and returning.
Copybara import of the project:

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6ad7c399e05182a543e50ed14f34b99a281155ce by Jaroslav Sevcik <jsevcik@nvidia.com>:

Emit no-op (AllocateBuffer custom-call)

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0f78007475921031549c8555ad56ed8903efe6cb by Jaroslav Sevcik <jsevcik@nvidia.com>:

Renamed allocate-buffer to nop in the test

Merging this change closes #10638

FUTURE_COPYBARA_INTEGRATE_REVIEW=https://github.com/openxla/xla/pull/10638 from jaro-sevcik:host-allocation-custom-call 0f78007475921031549c8555ad56ed8903efe6cb
