Modified SlavePty spawn_command macros to target windows/non-windows platforms

pty/src/lib.rs

@@ -164,7 +164,7 @@ impl_downcast!(ChildKiller);
 /// Can be used to spawn processes into the pty.
 pub trait SlavePty {
     /// Spawns the command specified by the provided CommandBuilder
-    #[cfg(unix)]
+    #[cfg(not(windows))]
     fn spawn_command(&self, cmd: CommandBuilder) -> Result<Box<dyn Child + Send + Sync>, Error>;
     /// Spawns a command specified by the provided CommandBuilder. 
     /// Accepts an Option<HANDLE> to a primary/impersonation token to spawn the process in the context of a different user. 

pty/src/serial.rs

@@ -109,7 +109,7 @@ struct Slave {
 }
 
 impl SlavePty for Slave {
-    #[cfg(unix)]
+    #[cfg(not(windows))]
     fn spawn_command(&self, cmd: CommandBuilder) -> anyhow::Result<Box<dyn Child + Send + Sync>> {
         ensure!(
             cmd.is_default_prog(),