name of `TestGame` executable clashes with directory name under Linux

[dlyongemallo]

On a Linux system (with PLATFORM_WINDOWS set to OFF), running cmake . followed by make results in the following error:

$ make
[ 11%] Building CXX object CMakeFiles/MiniEngine.dir/src/Platforms/Linux/LinuxWindow.cpp.o
[ 22%] Building CXX object CMakeFiles/MiniEngine.dir/src/Core/Game.cpp.o
[ 33%] Building CXX object CMakeFiles/MiniEngine.dir/src/Core/MiniTime.cpp.o
[ 44%] Building CXX object CMakeFiles/MiniEngine.dir/src/Core/Log/MiniLogger.cpp.o
[ 55%] Building CXX object CMakeFiles/MiniEngine.dir/src/Core/Log/Log.cpp.o
[ 66%] Building CXX object CMakeFiles/MiniEngine.dir/src/Core/Events/EventHandler.cpp.o
[ 77%] Linking CXX static library libMiniEngine.a
[ 77%] Built target MiniEngine
[ 88%] Building CXX object CMakeFiles/TestGame.dir/TestGame/TestGame.cpp.o
[100%] Linking CXX executable TestGame
/usr/bin/ld: cannot open output file TestGame: Is a directory
collect2: error: ld returned 1 exit status
make[2]: *** [CMakeFiles/TestGame.dir/build.make:98: TestGame] Error 1
make[1]: *** [CMakeFiles/Makefile2:111: CMakeFiles/TestGame.dir/all] Error 2
make: *** [Makefile:91: all] Error 2

The reason is that in CMakeLists.txt, the line project(TestGame) implies that the executable should be named TestGame, but a file (actually, a directory) with that name already exists. Renaming either the project or the directory allows the compilation to succeed.