ecm_process_po_files_as_qm: use own subdir ECMPoQm/ for build artifacts
Currently projects using ecm_install_po_files_as_qm(po) end up with the respective build dir countpart being cluttered with lots of subfolders, for all the language codes. Which makes navigating in the build dirs harder, also comes with a minimal risk of name clashes.
Placing all the build artifacts into a dedicated tool-namespaced subfolder avoids that. And having all related files in a separate dir might also improve inspecting the generation of these translation artifacts.
Before (by example of kjobwidgets):
.../build/kf6/frameworks/kjobwidgets$ ls
af CMakeCache.txt en he KF6JobWidgetsConfigVersion.cmake ms ru tg
ar CMakeDoxyfile.in en_GB hi KF6JobWidgetsQchTargets.cmake nb se th
as CMakeDoxygenDefaults.cmake eo hne kk nds si tr
autotests CMakeFiles es hr km ne sk tt
az cmake_install.cmake et hsb kn nl sl ug
be compile_commands.json eu hu ko nn sq uk
be@latin crh fa hy ku oc sr uz
bg cs fi ia lb or src uz@cyrillic
bin csb fr id lt pa sr@ijekavian vi
bn CTestTestfile.cmake fy install_manifest.txt lv pl sr@ijekavianlatin wa
bn_IN cy ga is mai prefix.sh sr@latin xh
br da gd it Makefile ps sv zh_CN
bs de gl ja mk pt ta zh_HK
ca ecm_uninstall.cmake gu ka ml pt_BR te zh_TW
ca@valencia el ha KF6JobWidgetsConfig.cmake mr ro testsAfter:
.../build/kf6/frameworks/kjobwidgets$ ls
autotests CMakeDoxyfile.in cmake_install.cmake ECMPoQm KF6JobWidgetsConfigVersion.cmake prefix.sh
bin CMakeDoxygenDefaults.cmake compile_commands.json ecm_uninstall.cmake KF6JobWidgetsQchTargets.cmake src
CMakeCache.txt CMakeFiles CTestTestfile.cmake KF6JobWidgetsConfig.cmake Makefile tests