Qt 6 based QtC: System() fails on long command line

Qt 5 based QtCreator works fine, but Qt 6 based QtCreator fails on system() with long command line in the .pro: 

qtPrepareTool(LRELEASE, lrelease)
command = $$LRELEASE -silent -removeidentical $$files($${SRC_PATH}/../../i18n/*.ts)
system($$command) | error("LRELEASE error: $$command")

.ts files are e.g. in the C:\Home\Projects\Test\SubTest\SomeLongDirectory\i18n\: da_DK.ts de_DE.ts en_US.ts es_ES.ts fi_FI.ts fr_FR.ts it_IT.ts ja_JP.ts ko_KR.ts nl_NL.ts nn_NO.ts pt_PT.ts sv_SE.ts zh_CN.ts