[boost] Building boost on osx 10.9 mavericks

Hi I could build boost 1.56 on macosx 10.9 for 10.9 but I do not manage to build boost on macosx 10.9 targeting macosx 10.8. It seems that darwin.jam does not recognize the installed SDKs such that I cannot use macosx-version feature. Now the developer resources are no longer in the /Developer folder but in /Applications/.../Xcode.app/Contents/Developer I tried to symlink this folder from /, I also tried a root=... argument to no avail. Any hint ? Tia Jérôme LAURENS