Split target_os = "nto" cfg by env so io-sock variants use TCP_KEEPIDLE

src/sys/unix.rs

   - wasm32-wasip2 
 target: 
   - aarch64-apple-darwin 
   - aarch64-apple-ios 
   - aarch64-apple-tvos 
   - aarch64-apple-visionos 
   - aarch64-apple-watchos 
   - aarch64-linux-android 
   - aarch64-unknown-freebsd 
   - aarch64-unknown-linux-gnu 
   - aarch64-unknown-linux-musl 
   - aarch64-unknown-linux-ohos 
   - aarch64-unknown-netbsd 
   - aarch64-unknown-openbsd 
   - aarch64-unknown-redox 
   - arm-linux-androideabi 
   - arm64_32-apple-watchos 
   - armv7-linux-androideabi 
   - armv7-sony-vita-newlibeabihf 
   - armv7-unknown-linux-ohos 
   - i686-linux-android 
   # Broken, see https://github.com/rust-lang/socket2/issues/539. 
   #- i686-unknown-hurd-gnu 
   - i686-unknown-linux-gnu 
   - sparcv9-sun-solaris 
   - x86_64-apple-darwin 
   - x86_64-apple-ios 
   - x86_64-pc-cygwin 
   - x86_64-pc-solaris 
   # Fails with: 
   # `rror calling dlltool 'x86_64-w64-mingw32-dlltool': No such file or 
   # directory (os error 2)`, build log: 
   # <https://github.com/rust-lang/socket2/actions/runs/9577808331/job/26406752150>. 
   #- x86_64-pc-windows-gnu 
   - x86_64-pc-windows-msvc 
   - x86_64-unknown-dragonfly 
   - x86_64-unknown-freebsd 
   - x86_64-unknown-fuchsia 
   - x86_64-unknown-illumos 
   - x86_64-unknown-linux-gnu 
   - x86_64-unknown-linux-musl 
   - x86_64-unknown-linux-ohos 
   - x86_64-unknown-netbsd 
   - x86_64-unknown-openbsd 
   - x86_64-unknown-redox 
   - wasm32-wasip2 
@@ -298,11 +298,17 @@ pub(crate) use libc::{TCP_KEEPCNT, TCP_KEEPINTVL};
 // See this type in the Windows file.
 pub(crate) type Bool = c_int;
 
+// QNX legacy io-pkt stack (nto70, nto71) exposes TCP_KEEPALIVE.
+// The newer io-sock stack (nto71_iosock, nto80) replaced it with the
+// BSD-style TCP_KEEPIDLE — handle both branches below.
 #[cfg(any(
     target_os = "ios",
     target_os = "visionos",
     target_os = "macos",
-    target_os = "nto",
+    all(
+        target_os = "nto",
+        any(target_env = "nto70", target_env = "nto71"),
+    ),
     target_os = "tvos",
     target_os = "watchos",
 ))]
@@ -312,7 +318,10 @@ use libc::TCP_KEEPALIVE as KEEPALIVE_TIME;
     target_os = "ios",
     target_os = "visionos",
     target_os = "macos",
-    target_os = "nto",
+    all(
+        target_os = "nto",
+        any(target_env = "nto70", target_env = "nto71"),
+    ),
     target_os = "openbsd",
     target_os = "tvos",
     target_os = "watchos",