Revert "Merge commit from fork"

This reverts commit 1e2b354456.

backend/local/lchmod_unix.go

@@ -1,41 +0,0 @@
-//go:build !windows && !plan9 && !js && !linux
-
-package local
-
-import (
-	"os"
-	"syscall"
-
-	"golang.org/x/sys/unix"
-)
-
-const haveLChmod = true
-
-// syscallMode returns the syscall-specific mode bits from Go's portable mode bits.
-//
-// Borrowed from the syscall source since it isn't public.
-func syscallMode(i os.FileMode) (o uint32) {
-	o |= uint32(i.Perm())
-	if i&os.ModeSetuid != 0 {
-		o |= syscall.S_ISUID
-	}
-	if i&os.ModeSetgid != 0 {
-		o |= syscall.S_ISGID
-	}
-	if i&os.ModeSticky != 0 {
-		o |= syscall.S_ISVTX
-	}
-	return o
-}
-
-// lChmod changes the mode of the named file to mode. If the file is a symbolic
-// link, it changes the link, not the target. If there is an error,
-// it will be of type *PathError.
-func lChmod(name string, mode os.FileMode) error {
-	// NB linux does not support AT_SYMLINK_NOFOLLOW as a parameter to fchmodat
-	// and returns ENOTSUP if you try, so we don't support this on linux
-	if e := unix.Fchmodat(unix.AT_FDCWD, name, syscallMode(mode), unix.AT_SYMLINK_NOFOLLOW); e != nil {
-		return &os.PathError{Op: "lChmod", Path: name, Err: e}
-	}
-	return nil
-}