vulkan: Fix gen_enum_to_str in out of tree builds
vulkan: Fix gen_enum_to_str in out of tree builds

In some configurations the util directory is created when building out
of tree, but not others. This patch ensures that it's created.

Signed-off-by: Dylan Baker <c26a678a04c601e0311b0d6006e67eee6ed19a8e@intel.com>
Reviewed-by: Matt Turner <789b315743a28dd066a4ba1459c35951c291d8a6@gmail.com>
Reviewed-and-Tested-by: Mike Lothian <a17fed27eaa842282862ff7c1b9c8395a26ac320@fireburn.co.uk>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler