Move format.cc from VULKAN_SRC to SRC

Support for building demos on a platform without Vulkan support

util/test/demos/CMakeLists.txt

@@ -4,7 +4,6 @@ set(PROJECT demos)
 
 set(VULKAN_SRC
         3rdparty/volk/volk.c
-        3rdparty/fmt/format.cc
         vk/vk_helpers.cpp
         vk/vk_test.cpp
         vk/vk_adv_cbuffer_zoo.cpp
@@ -100,6 +99,7 @@ set(OPENGL_SRC
         gl/gl_vertex_attr_zoo.cpp)
 
 set(SRC main.cpp
+        3rdparty/fmt/format.cc
         test_common.cpp
         texture_zoo.cpp)