Remove the NONE case from the OS enum.

Author: wildarch

src/main/java/com/google/devtools/build/lib/util/OS.java

@@ -23,7 +23,6 @@ public enum OS {
   FREEBSD("freebsd", "FreeBSD"),
   LINUX("linux", "Linux"),
   WINDOWS("windows", "Windows"),
-  NONE("none", "No OS"),
   UNKNOWN("unknown", "");
 
   private static final EnumSet<OS> POSIX_COMPATIBLE = EnumSet.of(DARWIN, FREEBSD, LINUX);