Issue when building for linux

[elKuzco]

Hi, i don't know if i do it wrong or not.
I have tried to build for debian, following instructions from Empty Epsilon.

When executing the command :

git clone https://github.com/daid/EmptyEpsilon.git
git clone https://github.com/daid/SeriousProton.git
cd EmptyEpsilon
mkdir -p _build
cd _build
cmake .. -G Ninja -DSERIOUS_PROTON_DIR=$PWD/../../SeriousProton/
ninja

i got this logs :

`CMake Warning (dev) at /usr/share/cmake-3.18/Modules/GNUInstallDirs.cmake:225 (message):
  Unable to determine default CMAKE_INSTALL_LIBDIR directory because no
  target architecture is known.  Please enable at least one language before
  including GNUInstallDirs.
Call Stack (most recent call first):
  CMakeLists.txt:12 (include)
This warning is for project developers.  Use -Wno-dev to suppress it.

-- The CXX compiler identification is GNU 10.2.1
-- The C compiler identification is GNU 10.2.1
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /usr/bin/c++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: /usr/bin/cc - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- EmptyEpsilon Version = 2021.6.13
CMake Warning (dev) at /usr/share/cmake-3.18/Modules/FindOpenGL.cmake:305 (message):
  Policy CMP0072 is not set: FindOpenGL prefers GLVND by default when
  available.  Run "cmake --help-policy CMP0072" for policy details.  Use the
  cmake_policy command to set the policy and suppress this warning.

  FindOpenGL found both a legacy GL library:

    OPENGL_gl_LIBRARY: /usr/lib/x86_64-linux-gnu/libGL.so

  and GLVND libraries for OpenGL and GLX:

    OPENGL_opengl_LIBRARY: /usr/lib/x86_64-linux-gnu/libOpenGL.so
    OPENGL_glx_LIBRARY: /usr/lib/x86_64-linux-gnu/libGLX.so

  OpenGL_GL_PREFERENCE has not been set to "GLVND" or "LEGACY", so for
  compatibility with CMake 3.10 and below the legacy GL library will be used.
Call Stack (most recent call first):
  CMakeLists.txt:56 (find_package)
This warning is for project developers.  Use -Wno-dev to suppress it.

-- Found OpenGL: /usr/lib/x86_64-linux-gnu/libOpenGL.so   
-- Crash Logger is 
-- Found SFML 2.5.1 in /usr/include
-- Performing Test _flag_supported
-- Performing Test _flag_supported - Failed
-- Crash Logger is: 
-- Found PythonInterp: /usr/bin/python (found version "2.7.18") 
-- Configuring done
-- Generating done
-- Build files have been written to: /tmp/EmptyEpsilon/_build
[4/455] Building CXX object CMakeFiles/EmptyEpsilon.dir/src/particleEffect.cpp.o
../src/particleEffect.cpp: In constructor ‘ParticleEngine::ParticleEngine()’:
../src/particleEffect.cpp:83:34: warning: comparison of integer expressions of different signedness: ‘int’ and ‘const size_t’ {aka ‘const long unsigned int’} [-Wsign-compare]
   83 |         for (auto quad = 0; quad < instances_per_draw; ++quad)
      |                             ~~~~~^~~~~~~~~~~~~~~~~~~~
../src/particleEffect.cpp: In member function ‘void ParticleEngine::doRender()’:
../src/particleEffect.cpp:162:46: warning: comparison of integer expressions of different signedness: ‘int’ and ‘long unsigned int’ [-Wsign-compare]
  162 |             for (auto instance = 0; instance < instance_count; ++instance)
      |                                     ~~~~~~~~~^~~~~~~~~~~~~~~~
../src/particleEffect.cpp:170:36: warning: comparison of integer expressions of different signedness: ‘int’ and ‘const size_t’ {aka ‘const long unsigned int’} [-Wsign-compare]
  170 |                 for (auto v = 0; v < vertices_per_instance; ++v)
      |                                  ~~^~~~~~~~~~~~~~~~~~~~~~~
[13/455] Building CXX object CMakeFiles/EmptyEpsilon.dir/src/gameGlobalInfo.cpp.o
FAILED: CMakeFiles/EmptyEpsilon.dir/src/gameGlobalInfo.cpp.o 
/usr/bin/c++ -DCONFIG_DIR=\"/share/emptyepsilon/\" -DRESOURCE_BASE_DIR=\"/share/emptyepsilon/\" -DSFML_NO_DEPRECATED_WARNINGS -DVERSION_NUMBER=2021613 -DWINDOW_TITLE=\"EmptyEpsilon\" -DWITH_DISCORD=0 -I../src -I/tmp/SeriousProton/src -I/tmp/SeriousProton/src/Box2D/.. -I/tmp/SeriousProton/src/lua/.. -I/tmp/SeriousProton/src/GL/.. -I/tmp/SeriousProton/src/libopus/include -I/tmp/SeriousProton/src/json11 -Iexternals/glm/glm/.. -Wall -Werror=return-type -std=gnu++17 -MD -MT CMakeFiles/EmptyEpsilon.dir/src/gameGlobalInfo.cpp.o -MF CMakeFiles/EmptyEpsilon.dir/src/gameGlobalInfo.cpp.o.d -o CMakeFiles/EmptyEpsilon.dir/src/gameGlobalInfo.cpp.o -c ../src/gameGlobalInfo.cpp
../src/gameGlobalInfo.cpp: In constructor ‘GameGlobalInfo::GameGlobalInfo()’:
../src/gameGlobalInfo.cpp:26:9: error: ‘nebula_info’ was not declared in this scope; did you mean ‘NebulaInfo’?
   26 |         nebula_info[n].vector = sf::Vector3f(random(-1, 1), random(-1, 1), random(-1, 1));
      |         ^~~~~~~~~~~
      |         NebulaInfo
[16/455] Building CXX object CMakeFiles/EmptyEpsilon.dir/src/GMActions.cpp.o
FAILED: CMakeFiles/EmptyEpsilon.dir/src/GMActions.cpp.o 
/usr/bin/c++ -DCONFIG_DIR=\"/share/emptyepsilon/\" -DRESOURCE_BASE_DIR=\"/share/emptyepsilon/\" -DSFML_NO_DEPRECATED_WARNINGS -DVERSION_NUMBER=2021613 -DWINDOW_TITLE=\"EmptyEpsilon\" -DWITH_DISCORD=0 -I../src -I/tmp/SeriousProton/src -I/tmp/SeriousProton/src/Box2D/.. -I/tmp/SeriousProton/src/lua/.. -I/tmp/SeriousProton/src/GL/.. -I/tmp/SeriousProton/src/libopus/include -I/tmp/SeriousProton/src/json11 -Iexternals/glm/glm/.. -Wall -Werror=return-type -std=gnu++17 -MD -MT CMakeFiles/EmptyEpsilon.dir/src/GMActions.cpp.o -MF CMakeFiles/EmptyEpsilon.dir/src/GMActions.cpp.o.d -o CMakeFiles/EmptyEpsilon.dir/src/GMActions.cpp.o -c ../src/GMActions.cpp
../src/GMActions.cpp: In member function ‘virtual void GameMasterActions::onReceiveClientCommand(int32_t, sf::Packet&)’:
../src/GMActions.cpp:106:35: error: no matching function for call to ‘ScriptSimpleCallback::call()’
  106 |                     callback.call();
      |                                   ^
In file included from /tmp/SeriousProton/src/engine.h:12,
                 from ../src/GMActions.h:4,
                 from ../src/GMActions.cpp:1:
/tmp/SeriousProton/src/scriptInterface.h:94:77: note: candidate: ‘template<class Return, class ... Args> std::conditional_t<is_void_v<Return>, void, std::optional<_Tp> > ScriptSimpleCallback::call(Args&& ...)’
   94 |     std::conditional_t<std::is_void_v<Return>, void, std::optional<Return>> call(Args&&... args)
      |                                                                             ^~~~
/tmp/SeriousProton/src/scriptInterface.h:94:77: note:   template argument deduction/substitution failed:
../src/GMActions.cpp:106:35: note:   couldn’t deduce template parameter ‘Return’
  106 |                     callback.call();
      |                                   ^
[22/455] Building CXX object CMakeFiles/EmptyEpsilon.dir/src/shipTemplate.cpp.o
ninja: build stopped: subcommand failed.`

Am i doing something wrong or is it a bug ?