Allow the backend to be configurable

CMakeLists.txt

@@ -1,6 +1,21 @@
 cmake_minimum_required(VERSION 3.0)
 project(GLdc)
 
+# set the default backend
+if(PLATFORM_DREAMCAST)
+    set(BACKEND "kospvr" CACHE STRING "Backend to use")
+else()
+    set(BACKEND "software" CACHE STRING "Backend to use")
+endif()
+
+# List of possible backends
+set_property(CACHE BACKEND PROPERTY STRINGS kospvr software)
+
+message("\nCompiling using backend: ${BACKEND}\n")
+
+string(TOUPPER ${BACKEND} BACKEND_UPPER)
+add_definitions(-DBACKEND_${BACKEND_UPPER})
+
 set(CMAKE_C_STANDARD 99)
 
 include_directories(include)

GL/platform.h

@@ -491,7 +491,7 @@ static inline void CompilePolyHeader(PolyHeader *dst, const PolyContext *src) {
     dst->d3 = dst->d4 = 0xffffffff;
 }
 
-#ifdef __DREAMCAST__
+#ifdef BACKEND_KOSPVR
 #include "platforms/sh4.h"
 #else
 #include "platforms/software.h"