tools/buildsystem_sanity_check: add check for APPLICATION in tests
tools/buildsystem_sanity_check: add check for APPLICATION in tests

This check verifies the APPLICATION variable is not set by tests application Makefiles. These applications should include the common test Makefile, where this variable is automatically set

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