linkinator: add silent flag.
linkinator: add silent flag.

This should reduce its output.

kvlsrg/bootstrap,stanwmusic/bootstrap,coliff/bootstrap,coliff/bootstrap,stanwmusic/bootstrap,tjkohli/bootstrap,peterblazejewicz/bootstrap,zalog/bootstrap,zalog/bootstrap,inway/bootstrap,GerHobbelt/bootstrap,kvlsrg/bootstrap,stanwmusic/bootstrap,m5o/bootstrap,GerHobbelt/bootstrap,inway/bootstrap,zalog/bootstrap,tjkohli/bootstrap,kvlsrg/bootstrap,m5o/bootstrap,twbs/bootstrap,GerHobbelt/bootstrap,peterblazejewicz/bootstrap,twbs/bootstrap,stanwmusic/bootstrap,inway/bootstrap,peterblazejewicz/bootstrap