Fix source code FMU CMake build

Author: perost

OMCompiler/SimulationRuntime/c/cmake/source_code_fmu_config.cmake

@@ -62,7 +62,8 @@ foreach(source_file ${SOURCE_FMU_COMMON_FILES_LIST})
   list(APPEND SOURCE_FMU_COMMON_FILES_LIST_QUOTED \"${source_file}\")
   get_filename_component(DEST_DIR ${source_file} DIRECTORY)
   if(CMAKE_VERSION VERSION_GREATER_EQUAL "3.20")
-    cmake_path(APPEND SOURCE_FMU_SOURCES_DEST_DIR "${SOURCE_FMU_SOURCES_DIR}" "${DEST_DIR}")
+    set(SOURCE_FMU_SOURCES_DEST_DIR "${SOURCE_FMU_SOURCES_DIR}")
+    cmake_path(APPEND SOURCE_FMU_SOURCES_DEST_DIR "${DEST_DIR}")
     cmake_path(NORMAL_PATH SOURCE_FMU_SOURCES_DEST_DIR)
   else()
     set(SOURCE_FMU_SOURCES_DEST_DIR "${SOURCE_FMU_SOURCES_DIR}/${DEST_DIR}")