unix: remove raw syscall from Getfsstat

Use libc version instead.

Update golang/go#17490

Change-Id: Ibcedccb9715961904d12fc85f69a7139b6c26658
Reviewed-on: https://go-review.googlesource.com/c/154660
Reviewed-by: Ian Lance Taylor <iant@golang.org>

unix/zsyscall_darwin_arm64.go

@@ -1708,6 +1708,17 @@ func Fstatfs(fd int, stat *Statfs_t) (err error) {
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
+func getfsstat(buf unsafe.Pointer, size uintptr, flags int) (n int, err error) {
+	r0, _, e1 := Syscall(SYS_GETFSSTAT, uintptr(buf), uintptr(size), uintptr(flags))
+	n = int(r0)
+	if e1 != 0 {
+		err = errnoErr(e1)
+	}
+	return
+}
+
+// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
+
 func Lstat(path string, stat *Stat_t) (err error) {
 	var _p0 *byte
 	_p0, err = BytePtrFromString(path)