/usr/lib/gcc/arm-none-eabi/7.4.0/../../../../arm-none-eabi/bin/ld: CMakeFiles/untitled2.elf.dir/Src/main.c.obj: in function `main':
/home/heinrich/CLionProjects/untitled2/Src/main.c:106: undefined reference to `sleep'
collect2: error: ld returned 1 exit status
make[3]: *** [CMakeFiles/untitled2.elf.dir/build.make:391: untitled2.elf] Fehler 1
make[2]: *** [CMakeFiles/Makefile2:73: CMakeFiles/untitled2.elf.dir/all] Fehler 2
make[1]: *** [CMakeFiles/Makefile2:85: CMakeFiles/untitled2.elf.dir/rule] Fehler 2
make: *** [Makefile:118: untitled2.elf] Fehler 2