nir: Make lowering gl_LocalInvocationIndex optional

Cc: "12.0" <mesa-stable@lists.freedesktop.org>
Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>

src/compiler/nir/nir.h

@@ -1682,6 +1682,8 @@ typedef struct nir_shader_compiler_options {
 
    /* Indicates that the driver only has zero-based vertex id */
    bool vertex_id_zero_based;
+
+   bool lower_cs_local_index_from_id;
 } nir_shader_compiler_options;
 
 typedef struct nir_shader_info {