build_variables.bzl: make XNNPACK_BACKEND_SRCS usable in BUCK (pytorch#13356)

Making the structure in this file mirror buck's worldview more closely
when it makes sense. pytorch#8268

Author: swolchok

backends/xnnpack/targets.bzl

@@ -1,4 +1,5 @@
 load("@fbsource//xplat/executorch/backends/xnnpack/third-party:third_party_libs.bzl", "third_party_dep")
+load("@fbsource//xplat/executorch/build:build_variables.bzl", "XNNPACK_BACKEND_BUCK_SRCS")
 load("@fbsource//xplat/executorch/build:runtime_wrapper.bzl", "get_aten_mode_options", "runtime")
 
 def _get_preprocessor_flags():
@@ -37,10 +38,7 @@ def define_common_targets():
         aten_suffix = "_aten" if aten_mode else ""
         runtime.cxx_library(
             name = "xnnpack_backend" + aten_suffix,
-            srcs = native.glob([
-                "runtime/*.cpp",
-                "runtime/profiling/*.cpp",
-            ]),
+            srcs = XNNPACK_BACKEND_BUCK_SRCS,
             headers = native.glob([
                 "runtime/*.h",
                 "runtime/profiling/*.h",

shim_et/xplat/executorch/build/build_variables.bzl

@@ -474,15 +474,17 @@ XNN_EXECUTOR_RUNNER_SRCS = [
     "extension/data_loader/file_data_loader.cpp",
 ]
 
-XNNPACK_BACKEND_SRCS = [
-    "backends/xnnpack/runtime/XNNCompiler.cpp",
-    "backends/xnnpack/runtime/XNNExecutor.cpp",
-    "backends/xnnpack/runtime/XNNHeader.cpp",
-    "backends/xnnpack/runtime/XNNPACKBackend.cpp",
-    "backends/xnnpack/runtime/XNNWeightsCache.cpp",
-    "backends/xnnpack/runtime/profiling/XNNProfiler.cpp",
+XNNPACK_BACKEND_BUCK_SRCS = [
+    "runtime/XNNCompiler.cpp",
+    "runtime/XNNExecutor.cpp",
+    "runtime/XNNHeader.cpp",
+    "runtime/XNNPACKBackend.cpp",
+    "runtime/XNNWeightsCache.cpp",
+    "runtime/profiling/XNNProfiler.cpp",
 ]
 
+XNNPACK_BACKEND_SRCS = ["backends/xnnpack/" + x for x in XNNPACK_BACKEND_BUCK_SRCS]
+
 XNNPACK_SCHEMA_SRCS = [
     "backends/xnnpack/serialization/runtime_schema.fbs",
 ]