std: enabling new netbsd (10) calls.

Introducing a new config for this purpose as NetBSD 9 or 8 will be still around
for a good while. For now, we re finally enabling sys::unix::rand::getrandom.

library/std/build.rs

@@ -3,6 +3,9 @@ use std::env;
 fn main() {
     println!("cargo:rerun-if-changed=build.rs");
     let target = env::var("TARGET").expect("TARGET was not set");
+    if target.contains("netbsd") && env::var("RUST_STD_NETBSD10").is_ok() {
+        println!("cargo:rust-cfg=netbsd10");
+    }
     if target.contains("linux")
         || target.contains("netbsd")
         || target.contains("dragonfly")

library/std/src/sys/unix/rand.rs

@@ -62,7 +62,7 @@ mod imp {
         unsafe { getrandom(buf.as_mut_ptr().cast(), buf.len(), libc::GRND_NONBLOCK) }
     }
 
-    #[cfg(any(target_os = "espidf", target_os = "horizon", target_os = "freebsd"))]
+    #[cfg(any(target_os = "espidf", target_os = "horizon", target_os = "freebsd", netbsd10))]
     fn getrandom(buf: &mut [u8]) -> libc::ssize_t {
         #[cfg(not(target_os = "freebsd"))]
         use libc::getrandom;
@@ -82,7 +82,8 @@ mod imp {
         target_os = "android",
         target_os = "espidf",
         target_os = "horizon",
-        target_os = "freebsd"
+        target_os = "freebsd",
+        netbsd10
     )))]
     fn getrandom_fill_bytes(_buf: &mut [u8]) -> bool {
         false
@@ -93,7 +94,8 @@ mod imp {
         target_os = "android",
         target_os = "espidf",
         target_os = "horizon",
-        target_os = "freebsd"
+        target_os = "freebsd",
+        netbsd10
     ))]
     fn getrandom_fill_bytes(v: &mut [u8]) -> bool {
         use crate::sync::atomic::{AtomicBool, Ordering};
@@ -229,7 +231,7 @@ mod imp {
 }
 
 // FIXME: once the 10.x release becomes the minimum, this can be dropped for simplification.
-#[cfg(target_os = "netbsd")]
+#[cfg(all(target_os = "netbsd", not(netbsd10)))]
 mod imp {
     use crate::ptr;
 

src/bootstrap/src/lib.rs

@@ -85,6 +85,7 @@ const EXTRA_CHECK_CFGS: &[(Option<Mode>, &str, Option<&[&'static str]>)] = &[
     (Some(Mode::Std), "no_sync", None),
     (Some(Mode::Std), "freebsd12", None),
     (Some(Mode::Std), "freebsd13", None),
+    (Some(Mode::Std), "netbsd10", None),
     (Some(Mode::Std), "backtrace_in_libstd", None),
     /* Extra values not defined in the built-in targets yet, but used in std */
     (Some(Mode::Std), "target_env", Some(&["libnx"])),