Fix feature gate for #[link_args(..)] attribute

[pnkfelix]

Fix feature gate for #[link_args(..)] attribute so that it will fire regardless of context of attribute.

See also #29596 and #43106

[rust-highfive]

r? @nikomatsakis

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[est31]

Should this be cratered?

[pnkfelix]

(agh that's almost certainly going to break tidy; will fix pronto)

[pnkfelix]

@est31 yeah probably, just to double-check that the impact is minimal

(because otherwise I suspect we would go through the more painful route of a warning cycle)

[nikomatsakis]

build fails:

---- [compile-fail] compile-fail/gated-link-args.rs stdout ----

[00:39:48] 	

[00:39:48] error: /checkout/src/test/compile-fail/gated-link-args.rs:28: unexpected "error": '28:1: 28:14: the name `main` is defined multiple times [E0428]'

[00:39:48] 

[00:39:48] error: 1 unexpected errors found, 0 expected errors not found

[00:39:48] status: exit code: 101

[00:39:48] command: /checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc /checkout/src/test/compile-fail/gated-link-args.rs -L /checkout/obj/build/x86_64-unknown-linux-gnu/test/compile-fail --target=x86_64-unknown-linux-gnu --error-format json -L /checkout/obj/build/x86_64-unknown-linux-gnu/test/compile-fail/gated-link-args.stage2-x86_64-unknown-linux-gnu.compile-fail.libaux -C prefer-dynamic -o /checkout/obj/build/x86_64-unknown-linux-gnu/test/compile-fail/gated-link-args.stage2-x86_64-unknown-linux-gnu -Crpath -O -Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers

[00:39:48] unexpected errors (from JSON output): [

[00:39:48]     Error {

[00:39:48]         line_num: 28,

[00:39:48]         kind: Some(

[00:39:48]             Error

[00:39:48]         ),

[00:39:48]         msg: "28:1: 28:14: the name `main` is defined multiple times [E0428]"

[00:39:48]     }

[00:39:48] ]

[nikomatsakis]

Crater builds complete. Running tests now.

[retep998]

Don't forget to test it as a crate level attribute #![link_args] instead of as an attribute on an item.

[nikomatsakis]

Here is the crater report:

Root regressions, sorted by rank:

• screenruster-saver-0.1.8 (before) (after) -- timeout
• tinyosc-0.0.3 (before) (after) -- timeout
• safe_authenticator-0.1.0 (before) (after) -- timeout
• taglib-0.2.0 (before) (after) -- timeout
• xml_writer-0.2.1 (before) (after) -- timeout
• pcap-rs-1.0.1 (before) (after) -- timeout
• ssd1325-0.1.0 (before) (after) -- timeout
• teapot-0.1.1 (before) (after) -- timeout

[nikomatsakis]

@bors r+

[bors]

📌 Commit c512dea has been approved by nikomatsakis

[bors]

⌛ Testing commit c512dea with merge eb9dfb8...

[bors]

☀️ Test successful - status-appveyor, status-travis
Approved by: nikomatsakis
Pushing eb9dfb8 to master...