Revert "cmake build: Disable clangpchmanagerbackend and refactoringbackend"

The change breaks the dev package:

The imported target "QtCreator::clangrefactoringbackend_lib" references
the file
"/home/qt/work/build/qtc_build/lib/qtcreator/libclangrefactoringbackend_lib.a"
but this file does not exist.

This reverts commit 20a6207459.

Change-Id: I68f3b6948bde611b9e5b841d1fde2b136877cbfc
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

cmake/QtCreatorAPI.cmake

@@ -541,7 +541,7 @@ endfunction()
 
 function(add_qtc_executable name)
   cmake_parse_arguments(_arg "SKIP_INSTALL;SKIP_TRANSLATION;ALLOW_ASCII_CASTS"
-    "DESTINATION;COMPONENT;BUILD_DEFAULT"
+    "DESTINATION;COMPONENT"
     "DEPENDS;DEFINES;INCLUDES;SOURCES;EXPLICIT_MOC;SKIP_AUTOMOC;EXTRA_TRANSLATIONS;PROPERTIES" ${ARGN})
 
   if ($_arg_UNPARSED_ARGUMENTS)
@@ -556,11 +556,7 @@ function(add_qtc_executable name)
   update_cached_list(__QTC_EXECUTABLES "${name}")
 
   string(TOUPPER "BUILD_EXECUTABLE_${name}" _build_executable_var)
-  if (DEFINED _arg_BUILD_DEFAULT)
-    set(_build_executable_default ${_arg_BUILD_DEFAULT})
-  else()
-    set(_build_executable_default ${BUILD_EXECUTABLES_BY_DEFAULT})
-  endif()
+  set(_build_executable_default ${BUILD_EXECUTABLES_BY_DEFAULT})
   if (DEFINED ENV{QTC_${_build_executable_var}})
     set(_build_executable_default "$ENV{QTC_${_build_executable_var}}")
   endif()