In OpenSolaris OS, when I run makefile generated by Eclipse CDT on the Linux OS, I get an error on the first -include line.
The same error was in FreeBSD, and was solved by executing gmake instead of make.
In OpenSolaris (just installed) gmake doesn't work (command not found).
What package should I install and how exactly, to build Linux-generated C++ project in OpenSolaris?
This tutorial might help you get a working / agreeable tool chain. I'm not sure what you already have, you may just need to install SUNWgmake to get up and running. Note, its just the tip of the portability iceberg.
If you can't find a GNU Make package, you can always download the source and build it yourself:
tar xjf make-VER.tar.bz2 # or tar xzf for .tar.gz
cd make-VER
./configure
make
make install # may need to run as root...