Do not enable LLD if we don't build host code for targets that opt into it

[Kobzol]

Should fix the problem mentioned in #147626 (comment).

r? @jieyouxu

[rustbot]

This PR modifies src/bootstrap/src/core/config.

If appropriate, please update CONFIG_CHANGE_HISTORY in src/bootstrap/src/utils/change_tracker.rs.

[rustbot]

jieyouxu is not on the review rotation at the moment.
They may take a while to respond.

[jieyouxu]

I do wonder if we should eventually transition to

we could also make the LLD config per-target, but that would complicate things

but this seems very reasonable in the meantime, thanks.

View changes since this review

[jieyouxu]

@bors r+ rollup=never

[bors]

📌 Commit a2c7e17 has been approved by jieyouxu

It is now in the queue for this repository.

[dpaoliello]

Validated that this change fixes the issue in our Arm64EC validation pipeline: we no longer need to set rust.lld=false.

[bors]

⌛ Testing commit a2c7e17 with merge 9a48790...

[rust-log-analyzer]

The job i686-msvc-1 failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)

error: test failed, to rerun pass `-p std --test sync`
Bootstrap failed while executing `test --stage 2 --skip=compiler --skip=src`
Build completed unsuccessfully in 2:13:29
make: *** [Makefile:112: ci-msvc-py] Error 1
  local time: Sun Oct 19 00:15:20 CUT 2025
  network time: Sun, 19 Oct 2025 00:15:20 GMT
##[error]Process completed with exit code 2.
##[group]Run echo "disk usage:"
echo "disk usage:"

[bors]

💔 Test failed - checks-actions

[Kobzol]

@bors retry Spurious.

[bors]

⌛ Testing commit a2c7e17 with merge c6efb90...

[bors]

☀️ Test successful - checks-actions
Approved by: jieyouxu
Pushing c6efb90 to master...

[github-actions]

What is this?

This is an experimental post-merge analysis report that shows differences in test outcomes between the merged PR and its parent PR.

Comparing 33cab8c (parent) -> c6efb90 (this PR)

Test differences

Show 2 test diffs

2 doctest diffs were found. These are ignored, as they are noisy.

Test dashboard

Run

cargo run --manifest-path src/ci/citool/Cargo.toml -- \
    test-dashboard c6efb9019b3169fc672248339dbbf13e6a134de3 --output-dir test-dashboard

And then open test-dashboard/index.html in your browser to see an overview of all executed tests.

Job duration changes

1. test-various: 4557.8s -> 7129.4s (56.4%)
2. pr-check-1: 1416.9s -> 1832.3s (29.3%)
3. dist-x86_64-apple: 7830.4s -> 6271.4s (-19.9%)
4. arm-android: 5389.0s -> 6237.0s (15.7%)
5. dist-aarch64-apple: 6402.5s -> 7245.5s (13.2%)
6. aarch64-apple: 8310.3s -> 7217.9s (-13.1%)
7. dist-riscv64-linux: 4685.4s -> 5203.1s (11.0%)
8. armhf-gnu: 4870.0s -> 5317.4s (9.2%)
9. dist-ohos-armv7: 4023.4s -> 4391.3s (9.1%)
10. aarch64-gnu-debug: 3624.0s -> 3939.1s (8.7%)

How to interpret the job duration changes?

Job durations can vary a lot, based on the actual runner instance
that executed the job, system noise, invalidated caches, etc. The table above is provided
mostly for t-infra members, for simpler debugging of potential CI slow-downs.

[rust-timer]

Finished benchmarking commit (c6efb90): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

This benchmark run did not return any relevant results for this metric.

Max RSS (memory usage)

Results (primary 2.1%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	2.1%	[2.1%, 2.1%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	2.1%	[2.1%, 2.1%]	1

Cycles

This benchmark run did not return any relevant results for this metric.

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 473.834s -> 472.659s (-0.25%)
Artifact size: 390.55 MiB -> 390.57 MiB (0.01%)