Merge #20890: doc: Add explicit macdeployqtplus dependencies install step

3e61b8c doc: Add explicit macdeployqtplus dependencies install step (Hennadii Stepanov)

Pull request description:

  This PR adds to macOS docs an explicit step to install `macdeployqtplus` script dependencies that are not part of the [Python Standard Library](https://docs.python.org/3/library/index.html):
  - https://pypi.org/project/ds-store/
  - https://pypi.org/project/mac-alias/

  This change is required on macOS 11 Big Sur:

  -  #20371
  - #20878

  Close #20878.

ACKs for top commit:
  fanquake:
    ACK 3e61b8c

Tree-SHA512: d177139ee142d47cb27ad878d721cafcd03403ef861965ff532d712da461416380ec5878f70accf223a552a1f1e65eedb1e0ad72cb7a96791f8a55536ce28645

Author: fanquake

doc/build-osx.md

@@ -30,6 +30,11 @@ If you want to build the disk image with `make deploy` (.dmg / optional), you ne
 brew install librsvg
 ```
 
+and [`macdeployqtplus`](../contrib/macdeploy/README.md) dependencies:
+```shell
+pip3 install ds_store mac_alias
+```
+
 The wallet support requires one or both of the dependencies ([*SQLite*](#sqlite) and [*Berkeley DB*](#berkeley-db)) in the sections below.
 To build Bitcoin Core without wallet, see [*Disable-wallet mode*](#disable-wallet-mode).