Force installing executable

So we don't fail if it is executed at the same time.

Makefile

@@ -50,7 +50,7 @@ dist:
 
 install: all
 	mkdir -p ${DESTDIR}${PREFIX}/bin
-	cp ${NAME}-${LAYOUT} ${DESTDIR}${PREFIX}/bin
+	cp -f ${NAME}-${LAYOUT} ${DESTDIR}${PREFIX}/bin
 	chmod 755 ${DESTDIR}${PREFIX}/bin/${NAME}-${LAYOUT}
 	mkdir -p "${DESTDIR}${MANPREFIX}/man1"
 	sed "s/VERSION/${VERSION}/g" < ${MAN1} > ${DESTDIR}${MANPREFIX}/man1/${MAN1}