make-snapshot: added missing options to usage

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@62583 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

tool/make-snapshot

@@ -32,6 +32,12 @@ options:
   -patch_file=PATCH     apply PATCH file after export
   -packages=PKG[,...]   make PKG packages (#{PACKAGES.keys.join(", ")})
   -digests=ALG[,...]    show ALG digests (#{DIGESTS.join(", ")})
+  -unicode_version=VER  Unicode version to generate encodings
+  -svn[=URL]            make snapshot from SVN repository
+                        (#{SVNURL})
+  -git[=URL]            make snapshot from GIT repository
+                        (#{GITURL})
+  -help, --help         show this message
 version:
   trunk, stable, branches/*, tags/*, X.Y, X.Y.Z, X.Y.Z-pL
 each versions may be followed by optional @revision.