st/mesa: release GLSL IR in LinkShader after it's not needed

Reviewed-by: Brian Paul <brianp@vmware.com>

src/mesa/state_tracker/st_glsl_to_tgsi.cpp

@@ -6149,6 +6149,10 @@ get_mesa_program(struct gl_context *ctx,
                              prog->OutputsWritten, 0ULL, prog->PatchOutputsWritten);
    count_resources(v, prog);
 
+   /* The GLSL IR won't be needed anymore. */
+   ralloc_free(shader->ir);
+   shader->ir = NULL;
+
    /* This must be done before the uniform storage is associated. */
    if (shader->Type == GL_FRAGMENT_SHADER &&
        (prog->InputsRead & VARYING_BIT_POS ||