Rollup merge of rust-lang#48005 - panicbit:env_unimpl_send_sync, r=al…

…excrichton

Unimplement Send/Sync for ::env::{Args,ArgsOs,Vars,VarsOs}

Fixes rust-lang#48004

src/libstd/env.rs

@@ -723,6 +723,12 @@ pub fn args_os() -> ArgsOs {
     ArgsOs { inner: sys::args::args() }
 }
 
+#[stable(feature = "env_unimpl_send_sync", since = "1.25.0")]
+impl !Send for Args {}
+
+#[stable(feature = "env_unimpl_send_sync", since = "1.25.0")]
+impl !Sync for Args {}
+
 #[stable(feature = "env", since = "1.0.0")]
 impl Iterator for Args {
     type Item = String;
@@ -754,6 +760,12 @@ impl fmt::Debug for Args {
     }
 }
 
+#[stable(feature = "env_unimpl_send_sync", since = "1.25.0")]
+impl !Send for ArgsOs {}
+
+#[stable(feature = "env_unimpl_send_sync", since = "1.25.0")]
+impl !Sync for ArgsOs {}
+
 #[stable(feature = "env", since = "1.0.0")]
 impl Iterator for ArgsOs {
     type Item = OsString;