doc: link to homebrew's troubleshooting page

Author: givanse

doc/build-osx.md

@@ -22,6 +22,7 @@ Then install [Homebrew](https://brew.sh).
 brew install automake berkeley-db4 libtool boost miniupnpc pkg-config python qt libevent qrencode
 ```
 
+If you run into issues, check [Homebrew's troubleshooting page](https://docs.brew.sh/Troubleshooting).
 See [dependencies.md](dependencies.md) for a complete overview.
 
 If you want to build the disk image with `make deploy` (.dmg / optional), you need RSVG: