boost: Drop unnecessary runtime dependency on Python

The only file that actually referred to the Python interpreter was
share/boost-build/example/customization/inline_file.py. So get rid of
the whole example directory.

pkgs/development/libraries/boost/1.55.nix

@@ -75,6 +75,7 @@ stdenv.mkDerivation {
     ./b2 -j$NIX_BUILD_CORES -sEXPAT_INCLUDE=${expat}/include -sEXPAT_LIBPATH=${expat}/lib --layout=${layout} variant=${variant} threading=${threading} link=${link} ${cflags} install${withToolset}
     rm $out/bin/bjam
     ln -s $out/bin/b2 $out/bin/bjam
+    rm -rf $out/share/boost-build/example
   '';
 
   crossAttrs = rec {