fix: --graph=foo.dot should not require graphviz installed (#10942)

### Description

I'm attempting to use `turbo ... --graph` in GHA to do some static
analysis of a very large repository. It's easy enough to extract
relevant patterns from a `.dot` file, but I wouldn't have expected to
need graphviz installed if I'm not actually using it.

I guess it turns out we _are_ using it, to do `dot - -T dot > out.dot`,
but this seems very odd when the `std::io::stdout()` case just outputs
directly. Seems like a bug.

### Testing Instructions

Edit your `PATH` to remove where graphviz is installed, then

```bash
turbo run build --graph foo.dot
```

Prior to this PR, you should get the error ` WARNING `turbo` uses
Graphviz to generate an image of your graph, but Graphviz isn't
installed on this machine.` and an empty `foo.dot`.
After this PR, you should end up with a populated dotfile and no
warning.

---------

Co-authored-by: Anthony Shew <[email protected]>

Author: blast-hardcheese

crates/turborepo-lib/src/run/graph_visualizer.rs

@@ -39,6 +39,13 @@ pub(crate) fn write_graph(
                 render_mermaid_graph(&filename, engine, single_package)?;
             } else if extension == "html" {
                 render_html(&filename, engine, single_package)?;
+            } else if extension == "dot" {
+                let mut opts = OpenOptions::new();
+                opts.truncate(true).create(true).write(true);
+                let file = filename
+                    .open_with_options(opts)
+                    .map_err(Error::GraphOutput)?;
+                render_dot_graph(file, engine, single_package)?;
             } else if let Ok(dot_path) = which("dot") {
                 let mut cmd = Command::new(dot_path);
                 cmd.stdin(Stdio::piped())