nix-shell: Fixes use with ruby shebangs.

The ported code in 80ebc553eca19dafc64c47420cd49ddd506bc9b7 was incorrectly ported.

```
-            $envCommand = "exec $execArgs $interpreter -e 'load(\"$script\")' -- ${\(join ' ', (map shellEscape, @savedArgs))}";
...
+                    envCommand = (format("exec %1% %2% -e 'load(\"%3%\") -- %4%") % execArgs % interpreter % script % joined.str()).str();
```

The single-quote finishing the small ruby snippet was lost in
translation.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/nix-build/nix-build.cc b/src/nix-build/nix-build.cc
index cf628519c..a63b3e07a 100755
--- a/src/nix-build/nix-build.cc
+++ b/src/nix-build/nix-build.cc
@@ -212,7 +212,7 @@ void mainWrapped(int argc, char * * argv)
                 // read the shebang to understand which packages to read from. Since
                 // this is handled via nix-shell -p, we wrap our ruby script execution
                 // in ruby -e 'load' which ignores the shebangs.
-                envCommand = (format("exec %1% %2% -e 'load(\"%3%\") -- %4%") % execArgs % interpreter % script % joined.str()).str();
+                envCommand = (format("exec %1% %2% -e 'load(\"%3%\")' -- %4%") % execArgs % interpreter % script % joined.str()).str();
             } else {
                 envCommand = (format("exec %1% %2% %3% %4%") % execArgs % interpreter % script % joined.str()).str();
             }