deps: Patch OpenBLAS with an operation-cancellation API
Adds a cancellation-token API to the OpenBLAS source build: a calling
thread binds a token (thread-local) before a BLAS call, any other thread
may cancel it, and the blocked level-3 drivers poll it between blocks,
abandoning the remaining compute while still executing every
synchronization point. A cancelled operation returns quickly with
unspecified output contents and the library stays consistent. This is
the library-side half of cancellable BLAS calls for the task
cancellation work; the runtime side registers a cancellation hook that
trips the token.
The patch is also staged as a git branch (kf/cancellation on a checkout
of OpenBLAS v0.3.33) for eventual submission upstream; a matching
binary build does not exist yet, so this requires
USE_BINARYBUILDER_OPENBLAS=0.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012nCkyKUguncLLJrH9K5o7m
