[ExecuTorch][WebGPU] Glob runtime/ops sources in CMakeLists

Pull Request resolved: #21005

Replace the hand-maintained explicit `WEBGPU_SRCS` op-handler list with `file(GLOB WEBGPU_OP_SRCS CONFIGURE_DEPENDS runtime/ops/*/*.cpp)` so adding a new op no longer requires editing this file (addresses review feedback). The five `runtime/*.cpp` sources and `runtime/ops/OperatorRegistry.cpp` (which sits directly under `ops/`, not a per-op subdir) stay explicit. `CONFIGURE_DEPENDS` re-globs at build time when op sources are added or removed.

The glob resolves to exactly the 40 op handlers the explicit list enumerated (verified set-equal) — no op added or dropped, and static-init registration is order-independent under `--whole-archive`.

Co-authored-with: Claude Code.
ghstack-source-id: 405026115
@exported-using-ghexport

Differential Revision: [D112482039](https://our.internmc.facebook.com/intern/diff/D112482039/)

Author: JCNTH

backends/webgpu/CMakeLists.txt

@@ -26,54 +26,18 @@ if(NOT TARGET vulkan_schema)
 endif()
 
 set(WEBGPU_SRCS
-    runtime/WebGPUBackend.cpp
-    runtime/WebGPUGraph.cpp
-    runtime/WebGPUDelegateHeader.cpp
-    runtime/WebGPUDevice.cpp
-    runtime/WebGPUQueryPool.cpp
-    runtime/ops/OperatorRegistry.cpp
-    runtime/ops/add/BinaryOp.cpp
-    runtime/ops/rms_norm/RmsNorm.cpp
-    runtime/ops/update_cache/UpdateCache.cpp
-    runtime/ops/sdpa/Sdpa.cpp
-    runtime/ops/select_as_symint/SelectAsSymint.cpp
-    runtime/ops/quantized_linear/QuantizedLinear.cpp
-    runtime/ops/quantized_linear/QuantizedLinearBackward.cpp
-    runtime/ops/mul/BinaryOp.cpp
-    runtime/ops/embedding_q4gsw/EmbeddingQ4gsw.cpp
-    runtime/ops/rope/RotaryEmbedding.cpp
-    runtime/ops/prepack/Prepack.cpp
-    runtime/ops/view_copy/ViewCopy.cpp
-    runtime/ops/select/Select.cpp
-    runtime/ops/sigmoid/UnaryOp.cpp
-    runtime/ops/squeeze/Squeeze.cpp
-    runtime/ops/unsqueeze/Unsqueeze.cpp
-    runtime/ops/slice/Slice.cpp
-    runtime/ops/permute/Permute.cpp
-    runtime/ops/cat/Cat.cpp
-    runtime/ops/index/Index.cpp
-    runtime/ops/sdpa_fd_decode/SdpaFdDecode.cpp
-    runtime/ops/mm/Mm.cpp
-    runtime/ops/fused_ce/FusedCe.cpp
-    runtime/ops/log_softmax/LogSoftmax.cpp
-    runtime/ops/softmax/Softmax.cpp
-    runtime/ops/bmm/Bmm.cpp
-    runtime/ops/reduce/Reduce.cpp
-    runtime/ops/div/BinaryOp.cpp
-    runtime/ops/sub/BinaryOp.cpp
-    runtime/ops/where/Where.cpp
-    runtime/ops/boolean_op/BooleanOp.cpp
-    runtime/ops/gather/Gather.cpp
-    runtime/ops/expand_copy/ExpandCopy.cpp
-    runtime/ops/fill/Fill.cpp
-    runtime/ops/dim_order/DimOrder.cpp
-    runtime/ops/linear/Linear.cpp
-    runtime/ops/embedding/Embedding.cpp
-    runtime/ops/adamw/AdamwStep.cpp
-    runtime/ops/quantized_linear/LinearDw.cpp
-    runtime/ops/quantized_linear/QuantizedLinearRequant.cpp
+    runtime/WebGPUBackend.cpp runtime/WebGPUGraph.cpp
+    runtime/WebGPUDelegateHeader.cpp runtime/WebGPUDevice.cpp
+    runtime/WebGPUQueryPool.cpp runtime/ops/OperatorRegistry.cpp
 )
 
+# Op handlers: glob so adding an op needs no CMakeLists edit. CONFIGURE_DEPENDS
+# re-globs at build time when op sources are added or removed.
+file(GLOB WEBGPU_OP_SRCS CONFIGURE_DEPENDS
+     "${CMAKE_CURRENT_SOURCE_DIR}/runtime/ops/*/*.cpp"
+)
+list(APPEND WEBGPU_SRCS ${WEBGPU_OP_SRCS})
+
 add_library(webgpu_backend ${WEBGPU_SRCS})
 
 # Verify committed *_wgsl.h match their *.wgsl (drift fails the build).