feat: add support for custom shells using an env var AMAZON_Q_CHAT_SHELL (#377)

Author: chaynabors

crates/chat-cli/src/cli/chat/tools/execute/unix.rs

@@ -27,8 +27,10 @@ pub async fn run_command<W: Write>(
     max_result_size: usize,
     mut updates: Option<W>,
 ) -> Result<CommandResult> {
+    let shell = std::env::var("AMAZON_Q_CHAT_SHELL").unwrap_or("bash".to_string());
+
     // We need to maintain a handle on stderr and stdout, but pipe it to the terminal as well
-    let mut child = tokio::process::Command::new("bash")
+    let mut child = tokio::process::Command::new(shell)
         .arg("-c")
         .arg(command)
         .stdin(Stdio::inherit())