Build problem in Ubuntu 17.10 with version tcl8.6

[ahanisch]

OS: Ubuntu 17.10
TCL: version 8.6 (this is the most recent version: https://packages.ubuntu.com/artful/tcl-dev)

If i run npm install, i got the following error:

../nodetk.cc:5:10: fatal error: tcl.h: No such file or directory
 #include <tcl.h>
          ^~~~~~~
compilation terminated.

This is because the file tcl.h is located in a subdirectory at /usr/include/tcl8.6/tcl.h. To fix this i set the include dir with export CXX="gcc -I/usr/include/tcl8.6". However then the compilation failed with:

../nodetk.cc: In function 'void TclEval(const Nan::FunctionCallbackInfo<v8::Value>&)':
../nodetk.cc:76:48: error: 'Tcl_Interp {aka struct Tcl_Interp}' has no member named 'result'
     info.GetReturnValue().Set(Nan::New(interp->result).ToLocalChecked());
                                                ^~~~~~

I could successfully build if i installed tcl8.5 and changed the include dir: export CXX="gcc -I/usr/include/tcl8.5".

So there seems to be a problem with tcl8.6 and the include dir in Ubuntu.