Make generation of .qm files silent

Avoid a lot of noise for the default builds, like

Updating 'C:/dev/qt/dev/msvc-2019-amd64/qtbase/translations/qtdeclarative_fr.qm'...
    Generated 306 translation(s) (306 finished and 0 unfinished)

Task-number: QTBUG-95975
Pick-to: 6.2
Change-Id: Id2df05b79be092e7a73241cabf10cae2cd96b169
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>

translations/CMakeLists.txt

@@ -143,7 +143,8 @@ set_source_files_properties(${ts_files} PROPERTIES OUTPUT_LOCATION "${qm_output_
 qt_add_lrelease(updateqm
     TS_FILES ${ts_files}
     NO_GLOBAL_TARGET
-    QM_FILES_OUTPUT_VARIABLE qm_files)
+    QM_FILES_OUTPUT_VARIABLE qm_files
+    OPTIONS "-silent")
 qt_install(FILES ${qm_files} DESTINATION "${INSTALL_TRANSLATIONSDIR}")
 
 # Custom target to add modified ts files to git