https://code.google.com/p/pkg-config-support-for-eclipse-cdt/
Rather than doing the usual:
Project Properties:
C/C++ Build -> Settings -> GCC C++ Compiler -> Miscellaneous -> Other flags -> `pkg-config gtkmm-3.0 –cflags`, etc.,
the following will work:
Project Properties:
C/C++ Build -> Settings -> Pkg-config -> gtkmm-3.0