[executorch] Add android-arm64 execution platform in shim & plumb it to extract_sources.py

Pull Request resolved: #5369

We need to tell Buck when we're building for Android, otherwise it will use the host configuration.
ghstack-source-id: 242793082
@exported-using-ghexport

Differential Revision: [D62671809](https://our.internmc.facebook.com/intern/diff/D62671809/)

Author: swolchok

build/Utils.cmake

@@ -184,11 +184,18 @@ function(extract_sources sources_file)
       set(executorch_root ${CMAKE_CURRENT_SOURCE_DIR})
     endif()
 
+    if(ANDROID_ABI)
+      if("${ANDROID_ABI}" STREQUAL "arm64-v8a")
+        set(target_platforms_arg "--target-platforms=shim//:android-arm64")
+      else()
+        message(FATAL_ERROR "Unsupported ANDROID_ABI setting ${ANDROID_ABI}. Please add it here!")
+      endif()
+    endif()
     execute_process(
       COMMAND
         ${PYTHON_EXECUTABLE} ${executorch_root}/build/extract_sources.py
         --config=${executorch_root}/build/cmake_deps.toml --out=${sources_file}
-        --buck2=${BUCK2}
+        --buck2=${BUCK2} ${target_platforms_arg}
       OUTPUT_VARIABLE gen_srcs_output
       ERROR_VARIABLE gen_srcs_error
       RESULT_VARIABLE gen_srcs_exit_code

build/extract_sources.py

@@ -11,7 +11,7 @@
 import re
 
 from enum import Enum
-from typing import Any, Optional, Sequence
+from typing import Any, List, Optional, Sequence
 
 from buck_util import Buck2Runner
 
@@ -96,7 +96,12 @@ def __init__(
             else:
                 self._config[k] = v
 
-    def get_sources(self, graph: "Graph", runner: Buck2Runner) -> frozenset[str]:
+    def get_sources(
+        self, graph: "Graph", runner: Buck2Runner, buck_args: Optional[List[str]]
+    ) -> frozenset[str]:
+        if buck_args is None:
+            buck_args = []
+
         if self._state == Target._InitState.READY:
             return self._sources
         # Detect cycles.
@@ -113,7 +118,7 @@ def get_sources(self, graph: "Graph", runner: Buck2Runner) -> frozenset[str]:
         )
 
         # Get the complete list of source files that this target depends on.
-        sources: set[str] = set(runner.run(["cquery", query]))
+        sources: set[str] = set(runner.run(["cquery", query] + buck_args))
 
         # Keep entries that match all of the filters.
         filters = [re.compile(p) for p in self._config.get("filters", [])]
@@ -128,7 +133,9 @@ def get_sources(self, graph: "Graph", runner: Buck2Runner) -> frozenset[str]:
         # its deps. Remove entries that are already covered by the transitive
         # set of dependencies.
         for dep in self._config.get("deps", []):
-            sources.difference_update(graph.by_name[dep].get_sources(graph, runner))
+            sources.difference_update(
+                graph.by_name[dep].get_sources(graph, runner, buck_args)
+            )
 
         self._sources = frozenset(sources)
         self._state = Target._InitState.READY
@@ -173,6 +180,9 @@ def parse_args() -> argparse.Namespace:
         metavar="file",
         help="Path to the file to generate.",
     )
+    parser.add_argument(
+        "--target-platforms", help="--target-platforms to pass to buck cquery, if any."
+    )
     return parser.parse_args()
 
 
@@ -199,8 +209,12 @@ def main():
     # Run the queries and get the lists of source files.
     target_to_srcs: dict[str, list[str]] = {}
     runner: Buck2Runner = Buck2Runner(args.buck2)
+    buck_args = []
+    if args.target_platforms:
+        buck_args = ["--target-platforms"]
+        buck_args.append(args.target_platforms)
     for name, target in graph.by_name.items():
-        target_to_srcs[name] = sorted(target.get_sources(graph, runner))
+        target_to_srcs[name] = sorted(target.get_sources(graph, runner, buck_args))
 
     # Generate the requested format.
     output: bytes

shim/BUCK

@@ -1,3 +1,4 @@
+load("@prelude//platforms:defs.bzl", "execution_platform")
 load("@prelude//toolchains:cxx.bzl", "system_cxx_toolchain")
 load("@prelude//toolchains:genrule.bzl", "system_genrule_toolchain")
 load("@prelude//toolchains:go.bzl", "system_go_toolchain")
@@ -55,3 +56,12 @@ remote_test_execution_toolchain(
     name = "remote_test_execution",
     visibility = ["PUBLIC"],
 )
+
+execution_platform(
+    name = "android-arm64",
+    cpu_configuration = "prelude//cpu:arm64",
+    os_configuration = "prelude//os:android",
+    # REVIEW: not sure if this is correct
+    use_windows_path_separators = host_info().os.is_windows,
+    visibility = ["PUBLIC"],
+)