ofborg: Always pass --show-trace, closes #19

ofborg/src/nix.rs

@@ -69,6 +69,7 @@ impl Nix {
             .env("HOME", "/homeless-shelter")
             .env("NIX_PATH", nixpath)
             .env("NIX_REMOTE", &self.remote)
+            .args(&["--show-trace"])
             .args(&["--option", "restrict-eval", "true"])
             .args(&["--option", "build-timeout", &format!("{}", self.build_timeout)])
             .args(&["--argstr", "system", &self.system])

ofborg/src/outpathdiff.rs

@@ -169,7 +169,6 @@ impl OutPaths    {
                 String::from("-qaP"),
                 String::from("--no-name"),
                 String::from("--out-path"),
-                String::from("--show-trace"),
                 String::from("--arg"), String::from("checkMeta"), check_meta,
             ],
             true