dist/tools/compile_commands: don't adds -nostdinc
dist/tools/compile_commands: don't adds -nostdinc

This fixes unintended side affects on rust compilation, which currently
relies on this tool to generate appropriate flags.

jasonatran/RIOT,RIOT-OS/RIOT,RIOT-OS/RIOT,jasonatran/RIOT,jasonatran/RIOT,RIOT-OS/RIOT,miri64/RIOT,kaspar030/RIOT,jasonatran/RIOT,kYc0o/RIOT,kYc0o/RIOT,ant9000/RIOT,jasonatran/RIOT,kaspar030/RIOT,ant9000/RIOT,kYc0o/RIOT,ant9000/RIOT,kaspar030/RIOT,RIOT-OS/RIOT,kaspar030/RIOT,kaspar030/RIOT,RIOT-OS/RIOT,miri64/RIOT,ant9000/RIOT,miri64/RIOT,ant9000/RIOT,kYc0o/RIOT,miri64/RIOT,kYc0o/RIOT,miri64/RIOT