supertux @0.6.2: build fails in Mono.framework is installed

[kencu (Ken)]

during the build of supertux the build fails if /Library/Frameworks/Mono.framework is installed:

[ 31%] Building CXX object squirrel/CMakeFiles/squirrel_static.dir/sqfuncstate.cpp.o
cd /opt/local/var/macports/build/_opt_macportsofficial_macports-ports_games_supertux/supertux/work/build/squirrel-prefix/src/squirrel-build/squirrel && /usr/bin/clang++ -D_SQ64 -I/opt/local/var/macports/build/_opt_macportsofficial_macports-ports_games_supertux/supertux/work/SuperTux-v0.6.2-Source/external/squirrel/include -pipe -Os -DNDEBUG -I/opt/local/include -stdlib=libc++ -isysroot/Library/Developer/CommandLineTools/SDKs/MacOSX10.14.sdk -O3 -DNDEBUG -isysroot /Library/Developer/CommandLineTools/SDKs/MacOSX10.14.sdk -mmacosx-version-min=10.14 -o CMakeFiles/squirrel_static.dir/sqfuncstate.cpp.o -c /opt/local/var/macports/build/_opt_macportsofficial_macports-ports_games_supertux/supertux/work/SuperTux-v0.6.2-Source/external/squirrel/squirrel/sqfuncstate.cpp
[ 33%] Building CXX object squirrel/CMakeFiles/squirrel.dir/sqbaselib.cpp.o
cd /opt/local/var/macports/build/_opt_macportsofficial_macports-ports_games_supertux/supertux/work/build/squirrel-prefix/src/squirrel-build/squirrel && /usr/bin/clang++ -D_SQ64 -Dsquirrel_EXPORTS -I/opt/local/var/macports/build/_opt_macportsofficial_macports-ports_games_supertux/supertux/work/SuperTux-v0.6.2-Source/external/squirrel/include -pipe -Os -DNDEBUG -I/opt/local/include -stdlib=libc++ -isysroot/Library/Developer/CommandLineTools/SDKs/MacOSX10.14.sdk -O3 -DNDEBUG -isysroot /Library/Developer/CommandLineTools/SDKs/MacOSX10.14.sdk -mmacosx-version-min=10.14 -fPIC -o CMakeFiles/squirrel.dir/sqbaselib.cpp.o -c /opt/local/var/macports/build/_opt_macportsofficial_macports-ports_games_supertux/supertux/work/SuperTux-v0.6.2-Source/external/squirrel/squirrel/sqbaselib.cpp
In file included from /opt/local/var/macports/build/_opt_macportsofficial_macports-ports_games_supertux/supertux/work/SuperTux-v0.6.2-Source/external/SDL_ttf/SDL_ttf.c:27:
/Library/Frameworks/Mono.framework/Headers/ft2build.h:56:10: fatal error: 'freetype/config/ftheader.h' file not found
#include <freetype/config/ftheader.h>
         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~

I can't say what exactly installed Mono.framework at the moment -- I have several things installed that might have done it, like Steam.app.

It was not obvious to me with 5 minutes looking how to make supertux} ignore Mono.framework so I disabled it for the supertux build, and that worked around the issue, although - obviously - not a proper solution to it.

cmake can set certain include directories as system directories to be searched before other system directories. I would imagine that adding the freetype2 include path to that "search before system list" might be a way.