glsl: Use textureGrad fallback when EXT_texture_shadow_lod is unsupported

src/shader_recompiler/profile.h

@@ -86,6 +86,7 @@ struct Profile {
     bool support_gl_nv_gpu_shader_5{};
     bool support_gl_amd_gpu_shader_half_float{};
     bool support_gl_vertex_viewport_layer{};
+    bool support_gl_texture_shadow_lod{};
 
     bool warp_size_potentially_larger_than_guest{};