adding software backend option (cmake)

CMakeOptions.txt

@@ -8,7 +8,7 @@ if(EMSCRIPTEN)
 endif()
 enum_option(PLATFORM "Desktop;Web;Android;Raspberry Pi;DRM;SDL" "Platform to build for.")
 
-enum_option(OPENGL_VERSION "OFF;4.3;3.3;2.1;1.1;ES 2.0;ES 3.0" "Force a specific OpenGL Version?")
+enum_option(OPENGL_VERSION "OFF;4.3;3.3;2.1;1.1;ES 2.0;ES 3.0;Software" "Force a specific OpenGL Version?")
 
 # Configuration options
 option(BUILD_EXAMPLES "Build the examples." ${PROJECT_IS_TOP_LEVEL})

cmake/LibraryConfigurations.cmake

@@ -122,6 +122,8 @@ if (NOT ${OPENGL_VERSION} MATCHES "OFF")
         set(GRAPHICS "GRAPHICS_API_OPENGL_ES2")
     elseif (${OPENGL_VERSION} MATCHES "ES 3.0")
         set(GRAPHICS "GRAPHICS_API_OPENGL_ES3")
+    elseif (${OPENGL_VERSION} MATCHES "Software")
+        set(GRAPHICS "GRAPHICS_API_OPENGL_11_SOFTWARE")
     endif ()
     if (NOT "${SUGGESTED_GRAPHICS}" STREQUAL "" AND NOT "${SUGGESTED_GRAPHICS}" STREQUAL "${GRAPHICS}")
         message(WARNING "You are overriding the suggested GRAPHICS=${SUGGESTED_GRAPHICS} with ${GRAPHICS}! This may fail.")