feat(docs): document building turbo from source (#7276)

docs/pages/repo/docs/support.mdx

@@ -3,7 +3,7 @@ title: Support Policy
 description: Our Support Policy for Turborepo and its ecosystem
 ---
 
-## Support Policy
+## Operating Systems
 
 `turbo` is generally supported on Debian-based Linux distributions, macOS, and
 Windows on both x86_64 and ARM 64 architectures. Specifically, we build and ship
@@ -21,6 +21,21 @@ are tested on Ubuntu, but we expect them to work on most [Debian-based][3]
 distros. Windows builds are tested on the [`windows-latest` runner][2] in GitHub
 Actions.
 
+### Unsupported Platforms
+
+Running `turbo` on unsupported platforms is possible by compiling from source. Instructions
+are available in the [contributing guide](https://github.com/vercel/turbo/blob/main/CONTRIBUTING.md).
+The built source is a single binary, so instead of installing and invoking via your Node.js package
+manager (e.g. `npm install turbo`), you will run the `turbo` binary directly:
+
+```bash
+/path/to/turbo run build
+```
+
+Since such invocations of `turbo` also defer to a locally installed `turbo` in your node_modules directory,
+if you're attempting to run `turbo` on a JavaScript project with `turbo` in package.json dependencies,
+use the `--skip-infer` flag to skip the deferal to the locally installed binary.
+
 ## Node.js Compatibility
 
 Most core `turbo` functionality (especially `turbo run`) does not depend on the