Fix Vulkan CI: remove duplicate SC_GFX_IMPLEMENTATION

Both sc_backend_vulkan.h and test_gfx.c compiled the sc_gfx_* dispatch functions, causing 'multiple definition' linker errors. Removed -DSC_GFX_IMPLEMENTATION from the test command — test_gfx.c defines it in source; sc_backend_vulkan.h only needs -DSC_BACKEND_VULKAN_IMPLEMENTATION for the Vulkan function implementations.

Author: amalxloop

.github/workflows/ci.yml

@@ -41,7 +41,6 @@ jobs:
       - name: Build and run Vulkan headless test
         run: |
           clang -I include -I tools -I backends \
-            -DSC_GFX_IMPLEMENTATION \
             -DSC_GFX_BACKEND_VULKAN -DSC_BACKEND_VULKAN_IMPLEMENTATION \
             -DSC_LAYOUT_IMPLEMENTATION -DSC_WIDGET_IMPLEMENTATION \
             -DSC_RUNTIME_IMPLEMENTATION -DSC_FONT_IMPLEMENTATION \