Use nix PR #2799 termios.rs changes: https://github.com/nix-rust/nix/pull/2799/files

--- build/amd64/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/nix-0.31.3/src/sys/termios.rs.old
+++ build/amd64/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/nix-0.31.3/src/sys/termios.rs
@@ -219,10 +219,10 @@
     /// Updates the wrapper values from the internal `libc::termios` data structure.
     pub(crate) fn update_wrapper(&mut self) {
         let termios = *self.inner.borrow_mut();
-        self.input_flags = InputFlags::from_bits_truncate(termios.c_iflag);
-        self.output_flags = OutputFlags::from_bits_truncate(termios.c_oflag);
+        self.input_flags = InputFlags::from_bits_retain(termios.c_iflag);
+        self.output_flags = OutputFlags::from_bits_retain(termios.c_oflag);
         self.control_flags = ControlFlags::from_bits_retain(termios.c_cflag);
-        self.local_flags = LocalFlags::from_bits_truncate(termios.c_lflag);
+        self.local_flags = LocalFlags::from_bits_retain(termios.c_lflag);
         self.control_chars = termios.c_cc;
         #[cfg(any(linux_android, target_os = "haiku"))]
         {
@@ -235,10 +235,10 @@
     fn from(termios: libc::termios) -> Self {
         Termios {
             inner: RefCell::new(termios),
-            input_flags: InputFlags::from_bits_truncate(termios.c_iflag),
-            output_flags: OutputFlags::from_bits_truncate(termios.c_oflag),
-            control_flags: ControlFlags::from_bits_truncate(termios.c_cflag),
-            local_flags: LocalFlags::from_bits_truncate(termios.c_lflag),
+            input_flags: InputFlags::from_bits_retain(termios.c_iflag),
+            output_flags: OutputFlags::from_bits_retain(termios.c_oflag),
+            control_flags: ControlFlags::from_bits_retain(termios.c_cflag),
+            local_flags: LocalFlags::from_bits_retain(termios.c_lflag),
             control_chars: termios.c_cc,
             #[cfg(any(linux_android, target_os = "haiku"))]
             line_discipline: termios.c_line,
@@ -460,9 +460,9 @@
     pub const VTIME: SpecialCharacterIndices = SpecialCharacterIndices::VEOL;
 }
 
-pub use libc::NCCS;
 #[cfg(any(bsd, linux_android, target_os = "aix", target_os = "solaris"))]
 pub use libc::_POSIX_VDISABLE;
+pub use libc::NCCS;
 
 libc_bitflags! {
     /// Flags for configuring the input mode of a terminal
@@ -947,3 +947,40 @@
     Errno::result(res).map(Pid::from_raw)
 }
 }
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use std::convert::TryFrom;
+
+    #[test]
+    fn try_from() {
+        assert_eq!(Ok(BaudRate::B0), BaudRate::try_from(libc::B0));
+        #[cfg(not(target_os = "haiku"))]
+        BaudRate::try_from(999999999).expect_err("assertion failed");
+        #[cfg(target_os = "haiku")]
+        BaudRate::try_from(99).expect_err("assertion failed");
+    }
+
+    #[test]
+    fn roundtrip_termios() {
+        // A fake termios including flag bits which we don't recognise.
+        #[allow(clippy::needless_update)]
+        let original = libc::termios {
+            c_iflag: 0xf00f,
+            c_oflag: 0xd00d,
+            c_cflag: 0x6642,
+            c_lflag: 0x1234,
+            c_cc: [0; NCCS],
+            ..unsafe { std::mem::zeroed() }
+        };
+
+        let mut attrs: Termios = original.into();
+        let before_update = attrs.get_libc_termios().to_owned();
+        attrs.update_wrapper();
+        let after_update = attrs.get_libc_termios().to_owned();
+
+        assert_eq!(before_update, original);
+        assert_eq!(after_update, original);
+    }
+}