Clean up generated files for ash,ramdisk,libutil,libc

lib/libminc/Makefile

@@ -77,6 +77,7 @@ CPPFLAGS.${i}+= -I${LIBCSRCDIR}/stdlib -I${LIBCSRCDIR}/include
 errlist.c: ${LIBCSRCDIR}/gen/errlist.awk \
 	   ${NETBSDSRCDIR}/include/sys/errno.h
 	cat ${NETBSDSRCDIR}/include/sys/errno.h | ${TOOL_SED} 's/(_SIGN//' | ${TOOL_AWK} -f ${LIBCSRCDIR}/gen/errlist.awk > ${.TARGET}
+CLEANFILES+=	errlist.c
 
 .for i in assert.c _errno.c errno.c _env.c errlist.c \
 	execle.c getprogname.c sleep.c time.c \