makefiles/docker.inc.mk: allow disabling color in docker
makefiles/docker.inc.mk: allow disabling color in docker

When compiling with CC_NOCOLOR=1, color were still used when
printing during compilation with `BUILD_IN_DOCKER=1`.

RIOT-OS/RIOT,mtausig/RIOT,kYc0o/RIOT,cladmi/RIOT,RIOT-OS/RIOT,toonst/RIOT,mtausig/RIOT,basilfx/RIOT,jasonatran/RIOT,ant9000/RIOT,mtausig/RIOT,yogo1212/RIOT,OlegHahm/RIOT,kaspar030/RIOT,josephnoir/RIOT,OTAkeys/RIOT,basilfx/RIOT,OlegHahm/RIOT,yogo1212/RIOT,basilfx/RIOT,OlegHahm/RIOT,toonst/RIOT,authmillenon/RIOT,kYc0o/RIOT,josephnoir/RIOT,miri64/RIOT,ant9000/RIOT,rfuentess/RIOT,jasonatran/RIOT,kYc0o/RIOT,rfuentess/RIOT,kaspar030/RIOT,mtausig/RIOT,RIOT-OS/RIOT,aeneby/RIOT,kYc0o/RIOT,authmillenon/RIOT,x3ro/RIOT,miri64/RIOT,kaspar030/RIOT,rfuentess/RIOT,smlng/RIOT,ant9000/RIOT,cladmi/RIOT,authmillenon/RIOT,miri64/RIOT,toonst/RIOT,smlng/RIOT,ant9000/RIOT,authmillenon/RIOT,OlegHahm/RIOT,kaspar030/RIOT,basilfx/RIOT,OlegHahm/RIOT,RIOT-OS/RIOT,cladmi/RIOT,cladmi/RIOT,x3ro/RIOT,aeneby/RIOT,yogo1212/RIOT,OTAkeys/RIOT,authmillenon/RIOT,x3ro/RIOT,basilfx/RIOT,josephnoir/RIOT,jasonatran/RIOT,miri64/RIOT,authmillenon/RIOT,josephnoir/RIOT,smlng/RIOT,OTAkeys/RIOT,smlng/RIOT,OTAkeys/RIOT,mtausig/RIOT,cladmi/RIOT,toonst/RIOT,toonst/RIOT,rfuentess/RIOT,ant9000/RIOT,aeneby/RIOT,miri64/RIOT,jasonatran/RIOT,yogo1212/RIOT,OTAkeys/RIOT,x3ro/RIOT,jasonatran/RIOT,yogo1212/RIOT,rfuentess/RIOT,aeneby/RIOT,yogo1212/RIOT,smlng/RIOT,aeneby/RIOT,x3ro/RIOT,RIOT-OS/RIOT,kYc0o/RIOT,kaspar030/RIOT,josephnoir/RIOT