I may be missing something but other toolchains seem to support thin_lto or other forms of LTO (https://github.com/tensorflow/tensorflow/blob/1843f39c11e42751837c62acfb74e1fe697353ef/third_party/toolchains/clang6/CROSSTOOL.tpl#L402 for example) -- it would be lovely to support that here. Or perhaps I'm mistaken: can someone suggest how I might enable LTO/pgo in general?