[libcalamares] Refactor translations-for-a-test CMake code

- turn the translations-QRC phase into a function, just in
  case other tests need translations as well.
- This CMake code might work as the base of translation-wrangling for
  plugins (externally).

src/libcalamares/CMakeLists.txt

@@ -215,29 +215,49 @@ calamares_add_test(
         ${geoip_src}
 )
 
-# Build up translations for this one test
-set( trans_file "localetest" )
-set( trans_infile ${CMAKE_CURRENT_BINARY_DIR}/${trans_file}.qrc )
-set( trans_outfile ${CMAKE_CURRENT_BINARY_DIR}/qrc_${trans_file}.cxx )
-set( calamares_i18n_qrc_content "<file>localetest_nl.qm</file>" )
-configure_file( ${CMAKE_SOURCE_DIR}/lang/calamares_i18n.qrc.in ${trans_infile} @ONLY )
-
-qt5_add_translation(QM_FILES "${CMAKE_CURRENT_SOURCE_DIR}/testdata/localetest_nl.ts")
-
-# Run the resource compiler (rcc_options should already be set)
-add_custom_command(
-    OUTPUT ${trans_outfile}
-    COMMAND "${Qt5Core_RCC_EXECUTABLE}"
-    ARGS ${rcc_options} --format-version 1 -name ${trans_file} -o ${trans_outfile} ${trans_infile}
-    MAIN_DEPENDENCY ${trans_infile}
-    DEPENDS ${QM_FILES}
-)
+function ( calamares_qrc_translations basename )
+    set( NAME ${ARGV0} )
+    set( options "" )
+    set( oneValueArgs SUBDIRECTORY OUTPUT_VARIABLE )
+    set( multiValueArgs LANGUAGES )
+    cmake_parse_arguments( _qrt "${options}" "${oneValueArgs}" "${multiValueArgs}" ${ARGN} )
+
+    if( NOT _qrt_OUTPUT_VARIABLE )
+        set( _qrt_OUTPUT_VARIABLE "qrc_translations_${basename}" )
+    endif()
+
+    set( translations_qrc_infile ${CMAKE_CURRENT_BINARY_DIR}/${basename}.qrc )
+    set( translations_qrc_outfile ${CMAKE_CURRENT_BINARY_DIR}/qrc_${basename}.cxx )
+
+    # Must use this variable name because of the @ substitution
+    set( calamares_i18n_qrc_content "" )
+    set( calamares_i18n_ts_filelist "" )
+    foreach( lang ${_qrt_LANGUAGES} )
+        string( APPEND calamares_i18n_qrc_content "<file>${basename}_${lang}.qm</file>" )
+        list( APPEND calamares_i18n_ts_filelist "${CMAKE_CURRENT_SOURCE_DIR}/${_qrt_SUBDIRECTORY}/${basename}_${lang}.ts" )
+    endforeach()
+
+    configure_file( ${CMAKE_SOURCE_DIR}/lang/calamares_i18n.qrc.in ${translations_qrc_infile} @ONLY )
+    qt5_add_translation(QM_FILES ${calamares_i18n_ts_filelist})
+
+    # Run the resource compiler (rcc_options should already be set)
+    add_custom_command(
+        OUTPUT ${translations_qrc_outfile}
+        COMMAND "${Qt5Core_RCC_EXECUTABLE}"
+        ARGS ${rcc_options} --format-version 1 -name ${basename} -o ${translations_qrc_outfile} ${translations_qrc_infile}
+        MAIN_DEPENDENCY ${translations_qrc_infile}
+        DEPENDS ${QM_FILES}
+    )
+
+    set( ${_qrt_OUTPUT_VARIABLE} ${translations_qrc_outfile} PARENT_SCOPE )
+endfunction()
 
+calamares_qrc_translations( localetest OUTPUT_VARIABLE localetest_qrc SUBDIRECTORY testdata LANGUAGES nl )
 calamares_add_test(
     libcalamareslocaletest
     SOURCES
         locale/Tests.cpp
-        ${trans_outfile}
+        ${localetest_qrc}
 )
 
 calamares_add_test(