Merge bitcoin#21988: doc: note that brew installed qt is not supported

33b0b26 doc: note that brew installed qt is not supported (Raul Siles)

Pull request description:

  picking up bitcoin#21791, the author has stated they [cannot squash](bitcoin#21791 (comment)).

  This is a useful note to prevent any issues from being opened up about this. The reason that both cannot co-exist and build bitcoin is stated [here](bitcoin#21791 (comment)):
  > ... the reason is sharing /usr/local/include/ and /usr/local/lib/ directories by both qt5 and qt6 installations.

  Changes from original PR:
  - slightly move the note up in this section, this placement seems more appropriate to me
  - drop "Note:"

  [PR Render](https://github.com/jarolrod/bitcoin/blob/33b0b26a03a401bd39b88931b69d162c3c538d31/doc/build-osx.md#qt)

ACKs for top commit:
  laanwj:
    LGTM ACK 33b0b26
  hebasto:
    ACK 33b0b26

Tree-SHA512: f9efac1921a7a33b5791a9f9f4bada4b5369d358fc42e9884c077bfb4dc3f273fdd4432ce012006a8009dfafb87e13bddd56c6336fe84b6133f4b22f849c289a

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/dashpay/dash/issues/7714).