build.go: Allow setting the output file name
build.go: Allow setting the output file name

byo/restic,byo/restic,ar-jan/restic,fawick/restic,restic/restic,fawick/restic,jayme-github/restic,middelink/restic,stuertz/restic,ar-jan/restic,middelink/restic,stuertz/restic,kurin/restic,jayme-github/restic,restic/restic,kurin/restic