Merge #12870: make clean removes src/qt/moc_ files

2ebad11 make clean removes src/qt/moc_ files (Sjors Provoost)

Pull request description:

  Prevents build errors when making e.g. the following switch:

  ```sh
  ./configure
  make
  make clean

  ./configure --with-gui=qt4
  make
  ```

Tree-SHA512: ec725dd6513e8d69398a4994f4b12a47f4e30401f421f8db7e398fca91b0f81bf9e4c566a23a37f229959f761daf6827a6d889f3b43faa05386ca083a8e392d7

Author: jonasschnelli

Makefile.am

@@ -293,6 +293,5 @@ clean-docs:
 	rm -rf doc/doxygen
 
 clean-local: clean-docs
-	rm -rf coverage_percent.txt test_bitcoin.coverage/ total.coverage/ test/tmp/ cache/ $(OSX_APP)
+	rm -rf coverage_percent.txt test_bitcoin.coverage/ total.coverage/ test/tmp/ cache/ $(OSX_APP) src/qt/moc_*
 	rm -rf test/functional/__pycache__ test/functional/test_framework/__pycache__ test/cache
-