glsl: add some data members to nir_variable

These will be used in the following patch.

Reviewed-by: Alejandro Piñeiro <apinheiro@igalia.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/28690>

src/compiler/nir/nir.h

@@ -616,6 +616,19 @@ typedef struct nir_variable {
        */
       int max_array_access;
 
+      /**
+       * Does this variable have an initializer?
+       *
+       * This is used by the linker to cross-validiate initializers of global
+       * variables.
+       */
+      unsigned has_initializer:1;
+
+      /**
+       * Is the initializer created by the compiler (glsl_zero_init)
+       */
+      unsigned is_implicit_initializer:1;
+
       /**
        * Is this varying used by transform feedback?
        *