The obvious workaround w.r.t. dtrace not finding the preprocessor is to install the command-line tools for xcode, which you can do from Xcode's preferences.

something else to try (before installing the commandline tools): add $(dirname $(xcrun -find cpp)) to the search path of the shell:

bash$ PATH="${PATH}:$(dirname $(xcrun -find cpp))"

This adds the directory in the Xcode bundle that contains the command-line tools to the search path of the shell, and might make it possible for dtrace to find the preprocessor (depending on how dtrace is coded). If that works this trick could be added to the build process, we already do something similar to locate the compiler in the configure script.