GH-137049: Stop creating an empty Modules/Setup.local when doing WASI builds

Author: brettcannon

Misc/NEWS.d/next/Build/2025-07-23-10-13-22.gh-issue-137049.FsfJWk.rst

@@ -0,0 +1,2 @@
+Stop creating an empty Modules/Setup.local when doing WASI builds as it's
+unnecessary.

Tools/wasm/wasi/__main__.py

@@ -22,9 +22,6 @@
 CROSS_BUILD_DIR = CHECKOUT / "cross-build"
 BUILD_DIR = CROSS_BUILD_DIR / "build"
 
-LOCAL_SETUP = CHECKOUT / "Modules" / "Setup.local"
-LOCAL_SETUP_MARKER = "# Generated by Tools/wasm/wasi.py\n".encode("utf-8")
-
 WASMTIME_VAR_NAME = "WASMTIME"
 WASMTIME_HOST_RUNNER_VAR = f"{{{WASMTIME_VAR_NAME}}}"
 
@@ -140,12 +137,6 @@ def build_python_is_pydebug():
 @subdir(BUILD_DIR, clean_ok=True)
 def configure_build_python(context, working_dir):
     """Configure the build/host Python."""
-    if LOCAL_SETUP.exists():
-        print(f"👍 {LOCAL_SETUP} exists ...")
-    else:
-        print(f"📝 Touching {LOCAL_SETUP} ...")
-        LOCAL_SETUP.write_bytes(LOCAL_SETUP_MARKER)
-
     configure = [os.path.relpath(CHECKOUT / 'configure', working_dir)]
     if context.args:
         configure.extend(context.args)
@@ -215,6 +206,10 @@ def configure_wasi_python(context, working_dir):
                         "https://github.com/WebAssembly/wasi-sdk and/or "
                         "specify via $WASI_SDK_PATH or --wasi-sdk")
 
+    setup_local = CHECKOUT / "Modules" / "Setup.local"
+    if setup_local.exists():
+        print(f"⚠️ {setup_local.relative_to(CHECKOUT)} exists")
+
     config_site = os.fsdecode(CHECKOUT / "Tools" / "wasm" / "wasi" / "config.site-wasm32-wasi")
 
     wasi_build_dir = working_dir.relative_to(CHECKOUT)
@@ -296,11 +291,6 @@ def clean_contents(context):
         print(f"🧹 Deleting {CROSS_BUILD_DIR} ...")
         shutil.rmtree(CROSS_BUILD_DIR)
 
-    if LOCAL_SETUP.exists():
-        with LOCAL_SETUP.open("rb") as file:
-            if file.read(len(LOCAL_SETUP_MARKER)) == LOCAL_SETUP_MARKER:
-                print(f"🧹 Deleting generated {LOCAL_SETUP} ...")
-
 
 def main():
     default_host_runner = (f"{WASMTIME_HOST_RUNNER_VAR} run "