A common pattern in Qt5 applications is to embed translations in the
executable using the qresource system. In this case, the list of
translation files is already available in the .qrc file and there's no
good reason to duplicate this info in meson.build.
Let compile_translations optionally take a qrc input, in which case it
will go straight to generating the relevant translations and
rcc-generated .cpp, and directly return the thing users actually care
about -- the .cpp for linking.
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