8149160: use StringJoiner in sjavac option handling Summary: Concatenation of strings now uses StringJoiner. Reviewed-by: alundblad, jjg Contributed-by: cushon@google.com

^build/
^dist/
nbproject/private/
^webrev
^.hgtip
^.bridge2
^.jib/
.DS_Store
.metadata/
.recommenders/