Remove i686-unknown-dragonfly target

[tuxillo]

DragonFly BSD removed support for i386 a while ago. It only supports x86_64 right now.

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @alexcrichton (or someone else) soon.

If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. Due to the way GitHub handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes.

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[tuxillo]

In reference to rust-lang/rust-forge#287
Not sure if I've missed anything, let me know and I'll refresh the PR.

[rust-highfive]

The job mingw-check of your PR failed (pretty log, raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

Click to expand the log.

2019-12-12T15:26:47.6346571Z ##[command]git remote add origin https://github.com/rust-lang/rust
2019-12-12T15:26:47.6565442Z ##[command]git config gc.auto 0
2019-12-12T15:26:47.6577191Z ##[command]git config --get-all http.https://github.com/rust-lang/rust.extraheader
2019-12-12T15:26:47.6631335Z ##[command]git config --get-all http.proxy
2019-12-12T15:26:47.6757337Z ##[command]git -c http.extraheader="AUTHORIZATION: basic ***" fetch --force --tags --prune --progress --no-recurse-submodules --depth=2 origin +refs/heads/*:refs/remotes/origin/* +refs/pull/67255/merge:refs/remotes/pull/67255/merge
---
2019-12-12T15:33:23.1877964Z     Checking rustc_feature v0.0.0 (/checkout/src/librustc_feature)
2019-12-12T15:33:23.1886448Z error[E0583]: file not found for module `i686_unknown_dragonfly`
2019-12-12T15:33:23.1887057Z    --> src/librustc_target/spec/mod.rs:401:32
2019-12-12T15:33:23.1887272Z     |
2019-12-12T15:33:23.1887571Z 401 |     ("i686-unknown-dragonfly", i686_unknown_dragonfly),
2019-12-12T15:33:23.1888089Z     |
2019-12-12T15:33:23.1888089Z     |
2019-12-12T15:33:23.1888429Z     = help: name the file either i686_unknown_dragonfly.rs or i686_unknown_dragonfly/mod.rs inside the directory "src/librustc_target/spec"
2019-12-12T15:33:23.1888731Z error: aborting due to previous error
2019-12-12T15:33:23.1888764Z 
2019-12-12T15:33:23.1889017Z For more information about this error, try `rustc --explain E0583`.
2019-12-12T15:33:23.1889264Z error: could not compile `rustc_target`.
---
2019-12-12T15:33:23.4814283Z   local time: Thu Dec 12 15:33:23 UTC 2019
2019-12-12T15:33:23.6325753Z   network time: Thu, 12 Dec 2019 15:33:23 GMT
2019-12-12T15:33:23.6332000Z == end clock drift check ==
2019-12-12T15:33:25.6883563Z 
2019-12-12T15:33:25.6940217Z ##[error]Bash exited with code '1'.
2019-12-12T15:33:25.6968577Z ##[section]Starting: Checkout
2019-12-12T15:33:25.6970096Z ==============================================================================
2019-12-12T15:33:25.6970146Z Task         : Get sources
2019-12-12T15:33:25.6970208Z Description  : Get sources from a repository. Supports Git, TfsVC, and SVN repositories.

I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact @TimNN. (Feature Requests)

[alexcrichton]

@bors: r+ rollup

[bors]

📌 Commit 0f47327 has been approved by alexcrichton