doc: note that brew installed qt is not supported

Author: raulsiles

doc/build-osx.md

@@ -138,6 +138,14 @@ Skip if you don't intend to use the GUI.
 brew install qt@5
 ```
 
+Ensure that the `qt@5` package is installed, not the `qt` package.
+If 'qt' is installed, the build process will fail.
+if installed, remove the `qt` package with the following command:
+
+``` bash
+brew uninstall qt
+```
+
 Note: Building with Qt binaries downloaded from the Qt website is not officially supported.
 See the notes in [#7714](https://github.com/bitcoin/bitcoin/issues/7714).