Fix stubtest failures for os.__init__ on windows (#4098)

stdlib/3/os/__init__.pyi

@@ -73,13 +73,14 @@ if sys.platform != 'win32':
     SCHED_RR: int  # some flavors of Unix
     SCHED_RESET_ON_FORK: int  # some flavors of Unix
 
-RTLD_LAZY: int
-RTLD_NOW: int
-RTLD_GLOBAL: int
-RTLD_LOCAL: int
-RTLD_NODELETE: int
-RTLD_NOLOAD: int
-RTLD_DEEPBIND: int
+if sys.platform != "win32":
+    RTLD_LAZY: int
+    RTLD_NOW: int
+    RTLD_GLOBAL: int
+    RTLD_LOCAL: int
+    RTLD_NODELETE: int
+    RTLD_NOLOAD: int
+    RTLD_DEEPBIND: int
 
 SEEK_SET: int
 SEEK_CUR: int
@@ -151,7 +152,8 @@ class _Environ(MutableMapping[AnyStr, AnyStr], Generic[AnyStr]):
     def __len__(self) -> int: ...
 
 environ: _Environ[str]
-environb: _Environ[bytes]
+if sys.platform != "win32":
+    environb: _Environ[bytes]
 
 if sys.platform != 'win32':
     confstr_names: Dict[str, int]
@@ -365,12 +367,15 @@ if sys.platform != 'win32':
 def getenv(key: Text) -> Optional[str]: ...
 @overload
 def getenv(key: Text, default: _T) -> Union[str, _T]: ...
-@overload
-def getenvb(key: bytes) -> Optional[bytes]: ...
-@overload
-def getenvb(key: bytes, default: _T = ...) -> Union[bytes, _T]: ...
+
+if sys.platform != "win32":
+    @overload
+    def getenvb(key: bytes) -> Optional[bytes]: ...
+    @overload
+    def getenvb(key: bytes, default: _T = ...) -> Union[bytes, _T]: ...
 def putenv(__name: Union[bytes, Text], __value: Union[bytes, Text]) -> None: ...
-def unsetenv(__name: Union[bytes, Text]) -> None: ...
+if sys.platform != "win32":
+    def unsetenv(__name: Union[bytes, Text]) -> None: ...
 
 # Return IO or TextIO
 def fdopen(fd: int, mode: str = ..., buffering: int = ..., encoding: Optional[str] = ...,
@@ -441,7 +446,9 @@ def access(
     follow_symlinks: bool = ...,
 ) -> bool: ...
 def chdir(path: _FdOrPathType) -> None: ...
-def fchdir(fd: int) -> None: ...
+
+if sys.platform != "win32":
+    def fchdir(fd: int) -> None: ...
 def getcwd() -> str: ...
 def getcwdb() -> bytes: ...
 def chmod(path: _FdOrPathType, mode: int, *, dir_fd: Optional[int] = ..., follow_symlinks: bool = ...) -> None: ...
@@ -468,11 +475,11 @@ def mkdir(path: _PathType, mode: int = ..., *, dir_fd: Optional[int] = ...) -> N
 if sys.platform != 'win32':
     def mkfifo(path: _PathType, mode: int = ..., *, dir_fd: Optional[int] = ...) -> None: ...  # Unix only
 def makedirs(name: _PathType, mode: int = ..., exist_ok: bool = ...) -> None: ...
-def mknod(path: _PathType, mode: int = ..., device: int = ..., *, dir_fd: Optional[int] = ...) -> None: ...
-def major(__device: int) -> int: ...
-def minor(__device: int) -> int: ...
-def makedev(__major: int, __minor: int) -> int: ...
-if sys.platform != 'win32':
+if sys.platform != "win32":
+    def mknod(path: _PathType, mode: int = ..., device: int = ..., *, dir_fd: Optional[int] = ...) -> None: ...
+    def major(__device: int) -> int: ...
+    def minor(__device: int) -> int: ...
+    def makedev(__major: int, __minor: int) -> int: ...
     def pathconf(path: _FdOrPathType, name: Union[str, int]) -> int: ...  # Unix only
 if sys.version_info >= (3, 6):
     def readlink(path: Union[AnyStr, PathLike[AnyStr]], *, dir_fd: Optional[int] = ...) -> AnyStr: ...
@@ -607,9 +614,14 @@ def popen(cmd: str, mode: str = ..., buffering: int = ...) -> _wrap_close: ...
 def spawnl(mode: int, file: _PathType, arg0: Union[bytes, Text], *args: Union[bytes, Text]) -> int: ...
 def spawnle(mode: int, file: _PathType, arg0: Union[bytes, Text],
             *args: Any) -> int: ...  # Imprecise sig
-def spawnv(mode: int, file: _PathType, args: List[Union[bytes, Text]]) -> int: ...
-def spawnve(mode: int, file: _PathType, args: List[Union[bytes, Text]],
-            env: _ExecEnv) -> int: ...
+if sys.platform != "win32":
+    def spawnv(mode: int, file: _PathType, args: List[Union[bytes, Text]]) -> int: ...
+    def spawnve(mode: int, file: _PathType, args: List[Union[bytes, Text]],
+                env: _ExecEnv) -> int: ...
+else:
+    def spawnv(__mode: int, __path: _PathType, __argv: List[Union[bytes, Text]]) -> int: ...
+    def spawnve(__mode: int, __path: _PathType, __argv: List[Union[bytes, Text]],
+                __env: _ExecEnv) -> int: ...
 def system(command: _PathType) -> int: ...
 def times() -> times_result: ...
 def waitpid(__pid: int, __options: int) -> Tuple[int, int]: ...
@@ -660,7 +672,7 @@ if sys.version_info >= (3, 6):
         def getrandom(size: int, flags: int = ...) -> bytes: ...
 def urandom(__size: int) -> bytes: ...
 
-if sys.version_info >= (3, 7):
+if sys.version_info >= (3, 7) and sys.platform != "win32":
     def register_at_fork(
         *,
         before: Optional[Callable[..., Any]] = ...,