Revert "use RWlock when accessing os::env #81850"

This reverts commit 354f19cf24, reversing
changes made to 0cfba2fd09.

library/std/src/sys_common/rwlock.rs

@@ -86,62 +86,3 @@ impl RWLock {
         self.0.destroy()
     }
 }
-
-// the cfg annotations only exist due to dead code warnings. the code itself is portable
-#[cfg(unix)]
-pub struct StaticRWLock(RWLock);
-
-#[cfg(unix)]
-impl StaticRWLock {
-    pub const fn new() -> StaticRWLock {
-        StaticRWLock(RWLock::new())
-    }
-
-    /// Acquires shared access to the underlying lock, blocking the current
-    /// thread to do so.
-    ///
-    /// The lock is automatically unlocked when the returned guard is dropped.
-    #[inline]
-    pub fn read_with_guard(&'static self) -> RWLockReadGuard {
-        // SAFETY: All methods require static references, therefore self
-        // cannot be moved between invocations.
-        unsafe {
-            self.0.read();
-        }
-        RWLockReadGuard(&self.0)
-    }
-
-    /// Acquires write access to the underlying lock, blocking the current thread
-    /// to do so.
-    ///
-    /// The lock is automatically unlocked when the returned guard is dropped.
-    #[inline]
-    pub fn write_with_guard(&'static self) -> RWLockWriteGuard {
-        // SAFETY: All methods require static references, therefore self
-        // cannot be moved between invocations.
-        unsafe {
-            self.0.write();
-        }
-        RWLockWriteGuard(&self.0)
-    }
-}
-
-#[cfg(unix)]
-pub struct RWLockReadGuard(&'static RWLock);
-
-#[cfg(unix)]
-impl Drop for RWLockReadGuard {
-    fn drop(&mut self) {
-        unsafe { self.0.read_unlock() }
-    }
-}
-
-#[cfg(unix)]
-pub struct RWLockWriteGuard(&'static RWLock);
-
-#[cfg(unix)]
-impl Drop for RWLockWriteGuard {
-    fn drop(&mut self) {
-        unsafe { self.0.write_unlock() }
-    }
-}