Fix a gcc warning in _sg_validate_pipeline_desc

sokol_gfx.h

@@ -7813,11 +7813,9 @@ _SOKOL_PRIVATE bool _sg_validate_pipeline_desc(const sg_pipeline_desc* desc) {
         SOKOL_VALIDATE(desc->shader.id != SG_INVALID_ID, _SG_VALIDATE_PIPELINEDESC_SHADER);
         const _sg_shader* shd = _sg_lookup_shader(&_sg.pools, desc->shader.id);
         SOKOL_VALIDATE(shd && shd->slot.state == SG_RESOURCESTATE_VALID, _SG_VALIDATE_PIPELINEDESC_SHADER);
-        bool buffers_cont = true;
         for (int buf_index = 0; buf_index < SG_MAX_SHADERSTAGE_BUFFERS; buf_index++) {
             const sg_buffer_layout_desc* l_desc = &desc->layout.buffers[buf_index];
             if (l_desc->stride == 0) {
-                buffers_cont = false;
                 continue;
             }
             SOKOL_VALIDATE((l_desc->stride & 3) == 0, _SG_VALIDATE_PIPELINEDESC_LAYOUT_STRIDE4);