Fix building of bjam itself after floating options change. Needed to make sure that we eat up the multi arg options if they exist.

[SVN r29239]

tools/build

@@ -1 +1 @@
-Subproject commit f97111f4cba93e4ce2a9c5c46a9581ef64835e21
+Subproject commit a97e4369a476454a1684c9b243b9a4a56ec5b259