hg: jdk9/sandbox/langtools: 8149160: use StringJoiner in sjavac option handling

[chris.hegarty at oracle.com]

Changeset: 8195be649661
Author:    alundblad
Date:      2016-02-10 14:22 +0100
URL:       http://hg.openjdk.java.net/jdk9/sandbox/langtools/rev/8195be649661

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

! src/jdk.compiler/share/classes/com/sun/tools/sjavac/options/Options.java
! test/tools/sjavac/JavacOptionPrep.java