When I run windeployqt on my application it shows that it's using lconvert to concatenate multiple translation files into one:

> C:\Qt\5.9.4\msvc2015_64\bin\windeployqt --release --no-compiler-runtime --verbose 10 my_app.exe

...
Creating qt_ar.qm...
Running: lconvert -o C:\Development\wireshark\cmbuild\run\RelWithDebInfo\translations\qt_ar.qm qtbase_ar.qm qtmultimedia_ar.qm
Creating qt_bg.qm...
Running: lconvert -o C:\Development\wireshark\cmbuild\run\RelWithDebInfo\translations\qt_bg.qm qtbase_bg.qm qtmultimedia_bg.qm
Creating qt_ca.qm...
Running: lconvert -o C:\Development\wireshark\cmbuild\run\RelWithDebInfo\translations\qt_ca.qm qtbase_ca.qm qtmultimedia_ca.qm
...

This creates a set of qt_XX.qm files in my translations directory:

> dir translations
Volume in drive C has no label.
Volume Serial Number is 68EB-7490

Directory of translations

01/24/2018 09:56 AM <DIR> .
01/24/2018 09:56 AM <DIR> ..
01/24/2018 12:00 PM 171,443 qt_ar.qm
01/24/2018 12:00 PM 178,970 qt_bg.qm
01/24/2018 12:00 PM 192,722 qt_ca.qm
...

However, "windeployqt --list" shows both the input translation files (which don't exist) and output files (which do exist):

> C:\Qt\5.9.4\msvc2015_64\bin\windeployqt --release --no-compiler-runtime --list relative my_app.exe

...
translations\qt_ar.qm
translations\qtbase_ar.qm
translations\qtmultimedia_ar.qm
translations\qt_bg.qm
translations\qtbase_bg.qm
translations\qtmultimedia_bg.qm
translations\qt_ca.qm
translations\qtbase_ca.qm
translations\qtmultimedia_ca.qm
...