glsl: Delete symbol table in post-link shaders

The symbol table in the linked shaders may contain references to
variables that were removed (e.g., unused uniforms).  Since it may
contain junk, there is no possible valid use.  Delete it and set the
pointer to NULL.

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

src/glsl/linker.cpp

@@ -1831,6 +1831,14 @@ done:
 
       /* Retain any live IR, but trash the rest. */
       reparent_ir(prog->_LinkedShaders[i]->ir, prog->_LinkedShaders[i]->ir);
+
+      /* The symbol table in the linked shaders may contain references to
+       * variables that were removed (e.g., unused uniforms).  Since it may
+       * contain junk, there is no possible valid use.  Delete it and set the
+       * pointer to NULL.
+       */
+      delete prog->_LinkedShaders[i]->symbols;
+      prog->_LinkedShaders[i]->symbols = NULL;
    }
 
    ralloc_free(mem_ctx);