Cleanup, to match build.sh structure and order.

Added detection of commands in PATH.
Added passthrough of extra args down to build.jam.


[SVN r16158]

tools/build

@@ -1 +1 @@
-Subproject commit 1b2c4af14be7fe215848ddafec3088cea1e93f8e
+Subproject commit 279c8ef3f8725e2f4727f48af7353433a15c68a1