Remove startswith('win') from autoninja and siso.

Windows can only be win32, and that holds to this day: https://docs.python.org/3.15/library/sys.html#sys.platform. Using this allows us to use better vscode integration of system checking and lines greyouts: https://screenshot.googleplex.com/8gkNyfPKMB9GPeU.

Change-Id: If9ab97bc30ab80df96b1aced0e78b0706a6a6964
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/7259617
Commit-Queue: Alex Ovsienko <ovsienko@google.com>
Reviewed-by: Junji Watanabe <jwata@google.com>

autoninja.py

@@ -150,7 +150,7 @@ def _quote_for_cmd(arg):
 
 def _print_cmd(cmd):
     shell_quoter = shlex.quote
-    if sys.platform.startswith("win"):
+    if sys.platform == "win32":
         shell_quoter = _quote_for_cmd
     print(*[shell_quoter(arg) for arg in cmd], file=sys.stderr)
 
@@ -250,7 +250,7 @@ def _check_reclient_cfgs(output_dir):
             cr_build_revision = f.read().strip()
     rewrapper_cfg_path = os.path.join(
         root_dir, "buildtools/reclient_cfgs/chromium-browser-clang/rewrapper_")
-    if sys.platform.startswith("win"):
+    if sys.platform == "win32":
         rewrapper_cfg_path += "windows.cfg"
     elif sys.platform == "darwin":
         rewrapper_cfg_path += "mac.cfg"
@@ -408,7 +408,7 @@ def _main_inner(input_args,
             # even if use_remoteexec=true is set.
             project = _siso_rbe_project(output_dir)
 
-        if sys.platform.startswith("win") or sys.platform == "darwin":
+        if sys.platform in ["win32", "darwin"]:
             _check_reclient_cfgs(output_dir)
 
         if _has_internal_checkout(output_dir):
@@ -613,7 +613,7 @@ def _main_inner(input_args,
 def _upload_ninjalog(args, exit_code, build_duration):
     # Run upload script without wait.
     creationflags = 0
-    if platform.system() == "Windows":
+    if sys.platform == "win32":
         creationflags = subprocess.CREATE_NEW_PROCESS_GROUP
     cmd = [
         sys.executable,
@@ -648,7 +648,7 @@ def _upload_sisolog(input_args: list[str], build_id: str):
 
         # Run upload script without wait.
         creationflags = 0
-        if platform.system() == "Windows":
+        if sys.platform == "win32":
             creationflags = subprocess.CREATE_NEW_PROCESS_GROUP
         cmd = [
             sys.executable,
@@ -687,7 +687,7 @@ def main(args):
     exit_code = 127
     telemetry_cfg = build_telemetry.load_config()
     should_collect_logs = telemetry_cfg.enabled()
-    if sys.platform.startswith("win") and len(args) == 2:
+    if sys.platform == "win32" and len(args) == 2:
         input_args = args[:1] + args[1].split()
     try:
         exit_code = _main_inner(input_args, build_id, telemetry_cfg)

siso.py

@@ -463,7 +463,7 @@ def main(args, telemetry_cfg: Optional[build_telemetry.Config] = None):
 
     signal.signal(signal.SIGINT, _ignore)
 
-    if not sys.platform.startswith('win'):
+    if sys.platform != "win32":
         signal.signal(signal.SIGTERM, lambda signum, frame: None)
 
     # On Windows the siso.bat script passes along the arguments enclosed in
@@ -472,7 +472,7 @@ def main(args, telemetry_cfg: Optional[build_telemetry.Config] = None):
     # detected, we need to split the argument. This means that arguments
     # containing actual spaces are not supported by siso.bat, but that is not a
     # real limitation.
-    if sys.platform.startswith('win') and len(args) == 2:
+    if sys.platform == "win32" and len(args) == 2:
         args = args[:1] + args[1].split()
 
     # macOS's python sets CPATH, LIBRARY_PATH, SDKROOT implicitly.