Re-export more os functions in posix, tweak availability on linux (#6529)

stdlib/os/__init__.pyi

@@ -575,8 +575,6 @@ if sys.platform != "win32":
     # Unix only
     def fchmod(fd: int, mode: int) -> None: ...
     def fchown(fd: int, uid: int, gid: int) -> None: ...
-    if sys.platform != "darwin":
-        def fdatasync(fd: FileDescriptorLike) -> None: ...  # Unix only, not Mac
     def fpathconf(__fd: int, __name: str | int) -> int: ...
     def fstatvfs(__fd: int) -> statvfs_result: ...
     def get_blocking(__fd: int) -> bool: ...
@@ -584,7 +582,8 @@ if sys.platform != "win32":
     def lockf(__fd: int, __command: int, __length: int) -> None: ...
     def openpty() -> tuple[int, int]: ...  # some flavors of Unix
     if sys.platform != "darwin":
-        def pipe2(flags: int) -> tuple[int, int]: ...  # some flavors of Unix
+        def fdatasync(fd: FileDescriptorLike) -> None: ...
+        def pipe2(__flags: int) -> tuple[int, int]: ...  # some flavors of Unix
         def posix_fallocate(fd: int, offset: int, length: int) -> None: ...
         def posix_fadvise(fd: int, offset: int, length: int, advice: int) -> None: ...
     def pread(__fd: int, __length: int, __offset: int) -> bytes: ...
@@ -632,17 +631,14 @@ def getcwd() -> str: ...
 def getcwdb() -> bytes: ...
 def chmod(path: _FdOrAnyPath, mode: int, *, dir_fd: int | None = ..., follow_symlinks: bool = ...) -> None: ...
 
-if sys.platform != "win32":
+if sys.platform != "win32" and sys.platform != "linux":
     def chflags(path: StrOrBytesPath, flags: int, follow_symlinks: bool = ...) -> None: ...  # some flavors of Unix
-    def chown(
-        path: _FdOrAnyPath, uid: int, gid: int, *, dir_fd: int | None = ..., follow_symlinks: bool = ...
-    ) -> None: ...  # Unix only
-
-if sys.platform != "win32":
-    # Unix only
-    def chroot(path: StrOrBytesPath) -> None: ...
     def lchflags(path: StrOrBytesPath, flags: int) -> None: ...
     def lchmod(path: StrOrBytesPath, mode: int) -> None: ...
+
+if sys.platform != "win32":
+    def chroot(path: StrOrBytesPath) -> None: ...
+    def chown(path: _FdOrAnyPath, uid: int, gid: int, *, dir_fd: int | None = ..., follow_symlinks: bool = ...) -> None: ...
     def lchown(path: StrOrBytesPath, uid: int, gid: int) -> None: ...
 
 def link(

stdlib/posix.pyi

@@ -103,6 +103,7 @@ if sys.platform != "win32":
         ctermid as ctermid,
         device_encoding as device_encoding,
         dup as dup,
+        dup2 as dup2,
         error as error,
         execv as execv,
         execve as execve,
@@ -212,6 +213,8 @@ if sys.platform != "win32":
         urandom as urandom,
         utime as utime,
         wait as wait,
+        wait3 as wait3,
+        wait4 as wait4,
         waitpid as waitpid,
         write as write,
         writev as writev,
@@ -231,6 +234,9 @@ if sys.platform != "win32":
             removexattr as removexattr,
             setxattr as setxattr,
         )
+    else:
+        from os import chflags as chflags, lchflags as lchflags, lchmod as lchmod
+
     if sys.platform != "darwin":
         from os import (
             POSIX_FADV_DONTNEED as POSIX_FADV_DONTNEED,
@@ -242,6 +248,7 @@ if sys.platform != "win32":
             fdatasync as fdatasync,
             getresgid as getresgid,
             getresuid as getresuid,
+            pipe2 as pipe2,
             posix_fadvise as posix_fadvise,
             posix_fallocate as posix_fallocate,
             sched_getaffinity as sched_getaffinity,