feat(tvix/tracing): optional progressbar

Disable the progressbar on default and provide a interface for
optionally enabling the progressbar.

Change-Id: I0e31b1957e80cf64a8dcf65c6ceb3713975b8220
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11861
Tested-by: BuildkiteCI
Reviewed-by: flokli <flokli@flokli.de>
Autosubmit: Simon Hauser <simon.hauser@helsinki-systems.de>

tvix/build/src/bin/tvix-build.rs

@@ -54,7 +54,9 @@ enum Commands {
 async fn main() -> Result<(), Box<dyn std::error::Error>> {
     let cli = Cli::parse();
 
-    let _ = tvix_tracing::TracingBuilder::default().level(cli.log_level);
+    let _ = tvix_tracing::TracingBuilder::default()
+        .level(cli.log_level)
+        .enable_progressbar();
 
     match cli.command {
         Commands::Daemon {