CMake: Calamares doesn't want -p in automoc

FIXES #1286

CMakeLists.txt

@@ -220,6 +220,8 @@ if( CMAKE_CXX_COMPILER_ID MATCHES "Clang" )
 
     set( CMAKE_SHARED_LINKER_FLAGS "-Wl,--no-undefined" )
 
+    # The path prefix is only relevant for CMake 3.16 and later, fixes #1286
+    set( CMAKE_AUTOMOC_PATH_PREFIX OFF )
     set( CALAMARES_AUTOMOC_OPTIONS "-butils/moc-warnings.h" )
     set( CALAMARES_AUTOUIC_OPTIONS --include utils/moc-warnings.h )
 else()