When exporting an AF3 model as FMU, all .c files are placed in the `sources/` directory besides `fmuTopEntry.c`. If the FMU compilation on other machines/architectures is wanted, this file is needed. See [FMUGeneratorExecutionTarget.java](https://git.fortiss.org/af3/af3/-/blob/master/org.fortiss.af3.component.ui/src/org/fortiss/af3/component/ui/generator/FMUGeneratorExecutionTarget.java#L173).