Merge pull request #46 from melange-re/gnu-patch

Add section about making sure patch is GNU patch

docs/installation/index.md

@@ -109,3 +109,34 @@ and add this snippet:
   "editor.defaultFormatter": "ocamllabs.ocaml-platform"
 }
 ```
+
+## Troubleshooting
+
+## Error while compiling OCaml
+
+If you get an error while compiling OCaml and it says something about not being
+able to find a file, then your `patch` binary probably isn't [GNU
+patch](https://savannah.gnu.org/projects/patch/). Run this in your shell:
+
+```bash
+patch --version
+```
+
+If it returns something like
+
+```text
+GNU patch 2.7.6
+Copyright (C) 2003, 2009-2012 Free Software Foundation, Inc.
+Copyright (C) 1988 Larry Wall
+
+License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
+This is free software: you are free to change and redistribute it.
+There is NO WARRANTY, to the extent permitted by law.
+
+Written by Larry Wall and Paul Eggert
+```
+
+then you're good to go. Otherwise, you need to install GNU patch and make sure
+that running `patch` will invoke it. How you do it depends on your operating
+system. For example, on Macs you can install from [Homebrew](https://brew.sh/)
+by running `brew install gpatch`.