Merge bitcoin/bitcoin#31361: cmake, qt: Use absolute paths for includes in MOC-generated files

6f4128e cmake, qt: Use absolute paths for includes in MOC-generated files (Hennadii Stepanov)

Pull request description:

  Fixes bitcoin/bitcoin#31145.

  From the `moc --help` output:
  ```
    -p <path>                         Path prefix for included file.
  ```

ACKs for top commit:
  laanwj:
    Tested ACK 6f4128e
  willcl-ark:
    tACK 6f4128e
  TheCharlatan:
    ACK 6f4128e
  BrandonOdiwuor:
    ACK 6f4128e

Tree-SHA512: f313698dec8976a7e0b3f26e6fd34ec041c253ccd75bdc0d7b272c3f786d77e83c35bc4607112960c65a378ec139f30a5187ce74498dce8b99a7349994846dee

Author: fanquake

src/qt/CMakeLists.txt

@@ -35,6 +35,7 @@ endfunction()
 #  - https://doc.qt.io/qt-5/cmake-manual.html
 
 set(CMAKE_AUTOMOC ON)
+set(CMAKE_AUTOMOC_MOC_OPTIONS "-p${CMAKE_CURRENT_SOURCE_DIR}")
 set(CMAKE_AUTORCC ON)
 set(CMAKE_AUTOUIC ON)
 set(CMAKE_AUTOUIC_SEARCH_PATHS forms)

src/qt/test/CMakeLists.txt

@@ -2,6 +2,8 @@
 # Distributed under the MIT software license, see the accompanying
 # file COPYING or https://opensource.org/license/mit/.
 
+set(CMAKE_AUTOMOC_MOC_OPTIONS "-p${CMAKE_CURRENT_SOURCE_DIR}")
+
 add_executable(test_bitcoin-qt
   apptests.cpp
   optiontests.cpp