rustc doesn't list `native` as a cpu option

[valarauca]

short summary of the bug

$ rustc -Ctarget-cpu=help

Doesn't list the native as an option.

I expected to see this happen:

I was informed, on reddit that rustc -C target-cpu=native was a valid option, but I could not see it listed in the help menu.

Meta

I see this issues on

rustc 1.22.0-nightly (088216fb9 2017-09-04) #current nightly
rustc 1.20.0 (f3d6973f4 2017-08-27) #stable

How to reproduce

$ rustc -C target-cpu=help | grep native | wc -l
0
$ rustc -C target-cpu=native
error: no input filename given

[mattico]

I've got a fix for this ready, just waiting for rustc to build...