Do not use ShaderVG until it's ready for use

CMakeLists.txt

@@ -95,7 +95,7 @@ option(ENABLE_RTI       "Set to ON to build SimGear with RTI support" OFF)
 option(ENABLE_GDAL      "Set to ON to build SimGear with GDAL support" OFF)
 option(ENABLE_TESTS     "Set to OFF to disable building SimGear's test applications" ON)
 option(ENABLE_SOUND     "Set to OFF to disable building SimGear's sound support" ON)
-option(USE_SHADERVG     "Set to ON to use SHaderVG instead of ShivaVG" ON)
+option(USE_SHADERVG     "Set to ON to use SHaderVG instead of ShivaVG" OFF)
 option(USE_AEONWAVE     "Set to ON to use AeonWave instead of OpenAL" ON)
 option(USE_OPENALSOFT   "Set to ON to use OpenAL from OpenAL-soft" OFF)