Deprecate ONCE_INIT in future 1.38 release

[sfackler]

Once::new() has been a stable const fn for a while now.

Closes #61746

[rust-highfive]

r? @bluss

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[sfackler]

r? @alexcrichton

[rust-highfive]

The job x86_64-gnu-llvm-6.0 of your PR failed on Travis (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.

travis_time:end:07b6d120:start=1560304861869235752,finish=1560304863831939339,duration=1962703587
$ git checkout -qf FETCH_HEAD
travis_fold:end:git.checkout

Encrypted environment variables have been removed for security reasons.
See https://docs.travis-ci.com/user/pull-requests/#pull-requests-and-security-restrictions
$ export SCCACHE_BUCKET=rust-lang-ci-sccache2
$ export SCCACHE_REGION=us-west-1
$ export GCP_CACHE_BUCKET=rust-lang-ci-cache
$ export AWS_ACCESS_KEY_ID=AKIA46X5W6CZEJZ6XT55
---
[00:27:47]    Compiling hashbrown v0.4.0
[00:27:50] error: use of deprecated item 'sync::once::ONCE_INIT': the `new` function is now preferred
[00:27:50]    --> src/libstd/sync/mod.rs:166:39
[00:27:50]     |
[00:27:50] 166 | pub use self::once::{Once, OnceState, ONCE_INIT};
[00:27:50]     |
[00:27:50]     = note: `-D deprecated` implied by `-D warnings`
[00:27:50] 
[00:27:52] error: aborting due to previous error

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)

[rust-highfive]

The job x86_64-gnu-llvm-6.0 of your PR failed on Travis (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.

travis_time:end:125c8c6b:start=1560312421231393291,finish=1560312423032216239,duration=1800822948
$ git checkout -qf FETCH_HEAD
travis_fold:end:git.checkout

Encrypted environment variables have been removed for security reasons.
See https://docs.travis-ci.com/user/pull-requests/#pull-requests-and-security-restrictions
$ export SCCACHE_BUCKET=rust-lang-ci-sccache2
$ export SCCACHE_REGION=us-west-1
$ export GCP_CACHE_BUCKET=rust-lang-ci-cache
$ export AWS_ACCESS_KEY_ID=AKIA46X5W6CZEJZ6XT55
---
[00:40:57]    Compiling rustc_mir v0.0.0 (/checkout/src/librustc_mir)
[00:40:58] error: use of deprecated item 'std::sync::ONCE_INIT': the `new` function is now preferred
[00:40:58]    --> src/librustc_metadata/dynamic_lib.rs:164:38
[00:40:58]     |
[00:40:58] 164 |         use std::sync::{Mutex, Once, ONCE_INIT};
[00:40:58]     |
[00:40:58]     = note: `-D deprecated` implied by `-D warnings`
[00:40:58] 
[00:40:58] error: use of deprecated item 'std::sync::ONCE_INIT': the `new` function is now preferred
[00:40:58] error: use of deprecated item 'std::sync::ONCE_INIT': the `new` function is now preferred
[00:40:58]    --> src/librustc_metadata/dynamic_lib.rs:165:29
[00:40:58]     |
[00:40:58] 165 |         static INIT: Once = ONCE_INIT;
[00:40:58]     |                             ^^^^^^^^^ help: replace the use of the deprecated item: `Once::new()`
[00:41:00] error: aborting due to 2 previous errors
[00:41:00] 
[00:41:01] error: Could not compile `rustc_metadata`.
[00:41:01] warning: build failed, waiting for other jobs to finish...
---
The command "stamp sh -x -c "$RUN_SCRIPT"" exited with 1.
travis_time:start:1cc294ee
$ date && (curl -fs --head https://google.com | grep ^Date: | sed 's/Date: //g' || true)
Wed Jun 12 04:54:04 UTC 2019
trap-oxgzobynhmm1/s-fd31q2bxq4-1tzpb2u-19ca4iajxr4qm
108532 ./src/llvm-project/lldb
102836 ./.git
98204 ./obj/build/x86_64-unknown-linux-gnu/stage1-std
98060 ./obj/build/x86_64-unknown-linux-gnu/stage0-std

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]

r=me w/ ci passing

[sfackler]

@bors r=alexcrichton

[bors]

📌 Commit d5df2a8 has been approved by alexcrichton

[Centril]

Failed in #61783 (comment), @bors r-

[sfackler]

I pushed the deprecation out one more release to avoid bootstrapping issues with clippy and cargo.

@bors r=alexcrichton

[bors]

📌 Commit 72e99f5 has been approved by alexcrichton