Ah, OK, glad you got that figured out. Could you clarify what you did to get it to find the right headers, for posterity? Others may run into the same issue, so if you used a particular config command that might be helpful.
i am no great programmer and i am not proud of it what i did.
and also i have no clue how CMake works. so what i did was: i moved away libwx-v2.8 headers from /usr/include/wx-2.8 and renamed /usr/include/wx-3.0 to /usr/include/wx-2.8
after that You only have to type: 'cmake -G "Unix Makefiles" ' to begin compilation in the directory You uncompressed the PCS2-master.zip ( https://github.com/scp-fs2open/PCS2/archive/master.zip
) (for me it was: /usr/src/PCS2-master/)
after compilation i made that reverse. i guess You MIGHT overcome this by removing libwx-2.8 headers, but i did not try that. i am sure this issue can be fixed in a more sophisticated way by someone who does understand CMake and fixes the CMake script.
my system is Debian 8.5 (Jessie) 32bit. i also had to install cmake v3.1+ from the jessie-backports repository. if this might help others, i can list some packages that i had and compiled with successfully:
ii libc6:i386 2.19-18+deb8u4 i386 GNU C Library: Shared libraries
ii libc6-dev:i386 2.19-18+deb8u4 i386 GNU C Library: Development Libraries and Header Files
ii cmake 3.6.2-2~bpo8+1 i386 cross-platform, open-source make system (from jessie-backports)
ii cmake-data 3.6.2-2~bpo8+1 all CMake data files (modules, templates and documentation) (from jessie-backports)
ii libwxbase3.0-0:i386 3.0.2-1+b1 i386 wxBase library (runtime) - non-GUI support classes of wxWidgets toolkit
ii libwxbase3.0-0-dbg:i386 3.0.2-1+b1 i386 debugging symbols for the wxBase library
ii libwxbase3.0-0-unofficial:i386 3.0.2-1.wheezy i386 wxBase library (runtime) - non-GUI support classes of wxWidgets toolkit
ii libwxbase3.0-dev 3.0.2-1+b1 i386 wxBase library (development) - non-GUI support classes of wxWidgets toolkit
ii libwxgtk3.0-0:i386 3.0.2-1+b1 i386 wxWidgets Cross-platform C++ GUI toolkit (GTK+ runtime)
ii libwxgtk3.0-0-dbg:i386 3.0.2-1+b1 i386 debugging symbols for the wxGTK GUI toolkit library
ii libwxgtk3.0-dev 3.0.2-1+b1 i386 wxWidgets Cross-platform C++ GUI toolkit (GTK+ development)
ii gcc 4:4.9.2-2 i386 GNU C compiler
ii gcc-4.9 4.9.2-10 i386 GNU C compiler
ii gcc-4.9-base:i386 4.9.2-10 i386 GCC, the GNU Compiler Collection (base package)
ii libgcc-4.9-dev:i386 4.9.2-10 i386 GCC support library (development files)
i am not sure if this is all You need, but i guess it is most of them. i hope that helps.