pythongh-145177: Add emscripten run --test, uses test args from config.toml (python#146160)

This allows us to change the test arguments from the python repo rather
than having to change buildmaster-config.

Co-authored-by: Russell Keith-Magee <russell@keith-magee.com>

Author: hoodmane

Platforms/emscripten/__main__.py

@@ -578,7 +578,10 @@ def run_emscripten_python(context):
     if args and args[0] == "--":
         args = args[1:]
 
-    os.execv(str(exec_script), [str(exec_script)] + args)
+    if context.test:
+        args = load_config_toml()["test-args"] + args
+
+    os.execv(str(exec_script), [str(exec_script), *args])
 
 
 def build_target(context):
@@ -695,6 +698,15 @@ def main():
         "run",
         help="Run the built emscripten Python",
     )
+    run.add_argument(
+        "--test",
+        action="store_true",
+        default=False,
+        help=(
+            "If passed, will add the default test arguments to the beginning of the command. "
+            "Default arguments loaded from Platforms/emscripten/config.toml"
+        )
+    )
     run.add_argument(
         "args",
         nargs=argparse.REMAINDER,
@@ -704,6 +716,7 @@ def main():
         )
     )
     add_cross_build_dir_option(run)
+
     clean = subcommands.add_parser(
         "clean", help="Delete files and directories created by this script"
     )

Platforms/emscripten/config.toml

@@ -3,6 +3,14 @@
 # Python versions.
 emscripten-version = "4.0.12"
 node-version = "24"
+test-args = [
+    "-m", "test",
+    "-v",
+    "-uall",
+    "--rerun",
+    "--single-process",
+    "-W",
+]
 
 [libffi]
 url = "https://github.com/libffi/libffi/releases/download/v{version}/libffi-{version}.tar.gz"