Updates from comments

Author: simlay

library/std/src/sys/pal/unix/fd.rs

@@ -45,13 +45,9 @@ const READ_LIMIT: usize = libc::ssize_t::MAX as usize;
 #[cfg(any(
     target_os = "dragonfly",
     target_os = "freebsd",
-    target_os = "ios",
-    target_os = "tvos",
-    target_os = "macos",
     target_os = "netbsd",
     target_os = "openbsd",
-    target_os = "watchos",
-    target_os = "visionos",
+    target_vendor = "apple",
 ))]
 const fn max_iov() -> usize {
     libc::IOV_MAX as usize
@@ -72,17 +68,13 @@ const fn max_iov() -> usize {
     target_os = "dragonfly",
     target_os = "emscripten",
     target_os = "freebsd",
-    target_os = "ios",
-    target_os = "tvos",
     target_os = "linux",
-    target_os = "macos",
     target_os = "netbsd",
     target_os = "nto",
     target_os = "openbsd",
     target_os = "horizon",
     target_os = "vita",
-    target_os = "watchos",
-    target_os = "visionos",
+    target_vendor = "apple",
 )))]
 const fn max_iov() -> usize {
     16 // The minimum value required by POSIX.
@@ -201,14 +193,10 @@ impl FileDesc {
         target_os = "fuchsia",
         target_os = "hurd",
         target_os = "illumos",
-        target_os = "ios",
-        target_os = "tvos",
         target_os = "linux",
-        target_os = "macos",
         target_os = "netbsd",
         target_os = "openbsd",
-        target_os = "watchos",
-        target_os = "visionos",
+        target_vendor = "apple",
     )))]
     pub fn read_vectored_at(&self, bufs: &mut [IoSliceMut<'_>], offset: u64) -> io::Result<usize> {
         io::default_read_vectored(|b| self.read_at(b, offset), bufs)
@@ -362,14 +350,10 @@ impl FileDesc {
         target_os = "fuchsia",
         target_os = "hurd",
         target_os = "illumos",
-        target_os = "ios",
-        target_os = "tvos",
         target_os = "linux",
-        target_os = "macos",
         target_os = "netbsd",
         target_os = "openbsd",
-        target_os = "watchos",
-        target_os = "visionos",
+        target_vendor = "apple",
     )))]
     pub fn write_vectored_at(&self, bufs: &[IoSlice<'_>], offset: u64) -> io::Result<usize> {
         io::default_write_vectored(|b| self.write_at(b, offset), bufs)