Add support for xray in aarch64 unknown none target

[odlot]

I am currently working on an embedded project and use the target aarch64-unknown-none, which I want to profile.
I found the following compiler flag -Z instrument-xray (https://doc.rust-lang.org/unstable-book/compiler-flags/instrument-xray.html) available and I locally built a toolchain that sets the supports_xray: true option in TargetOptions for compiler/rustc_target/src/spec/targets/aarch64_unknown_none.rs.
Using this toolchain in rustup I am able to use the instrumentation pass and I verified that the disassembly looks as what I want.
I understand that it isn't available upstream while being supported due to the separate runtime library which has to be linked (e.g., https://www.llvm.org/docs/XRay.html#xray-runtime-library), which is not available for aarch64-unknown-none.
I argue that someone who cross-compiles for aarch64-unknown-none would be okay with writing a separate runtime library themselves, which I intend to do.
As far as I understood it is not necessarily required to have a runtime library at this point, i.e., the user of this API should link it, e.g., from their build.rs file using cargo::rustc-link-lib=LIB if there is an XRay LIB available for the respective target, e.g., clang+llvm-19.1.1-aarch64-linux-gnu/lib/clang/19/lib/aarch64-unknown-linux-gnu/libclang_rt.xray-fdr.a (which afaik there isn't for aarch64-unknown-none) and do "configuration as code" of XRay's options.
It should not be part of the compiler, because the instrumentation and the runtime library are completely decoupled. One can modify the instrumented code by the compiler pass however one wants to, this again pushes me into the direction of telling the developer to bring his own runtime library.

I would like to bring my change that enables this instrumentation back into upstream to facilitate my developer experience.

[rustbot]

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spellchecking files
building external tool typos from package typos-cli@1.38.1
finished building tool typos
npm WARN deprecated puppeteer@22.15.0: < 24.10.2 is no longer supported
npm ERR! code 127
npm ERR! git dep preparation failed
npm ERR! command /node/bin/node /node/lib/node_modules/npm/bin/npm-cli.js install --force --cache=/home/user/.npm --prefer-offline=false --prefer-online=false --offline=false --no-progress --no-save --no-audit --include=dev --include=peer --include=optional --no-package-lock-only --no-dry-run
npm ERR! npm WARN using --force Recommended protections disabled.
npm ERR! npm WARN deprecated inflight@1.0.6: This module is not supported, and leaks memory. Do not use it. Check out lru-cache if you want a good and tested way to coalesce async requests by a key value, which is much more comprehensive and powerful.
npm ERR! npm WARN deprecated glob@7.2.3: Glob versions prior to v9 are no longer supported
npm ERR! npm WARN deprecated glob@7.2.3: Glob versions prior to v9 are no longer supported
npm ERR! npm WARN deprecated readdir-scoped-modules@1.1.0: This functionality has been moved to @npmcli/fs
npm ERR! npm WARN deprecated debuglog@1.0.1: Package no longer supported. Contact Support at https://www.npmjs.com/support for more info.
npm ERR! npm WARN deprecated read-package-json@2.1.2: This package is no longer supported. Please use @npmcli/package-json instead.
npm ERR! npm WARN deprecated read-installed@4.0.3: This package is no longer supported.
npm ERR! npm ERR! code 127
npm ERR! npm ERR! path /home/user/.npm/_cacache/tmp/git-cloneXXXXXXxJAtle/node_modules/rollup
npm ERR! npm ERR! command failed
npm ERR! npm ERR! command sh -c patch-package
npm ERR! npm ERR! sh: 1: patch-package: not found
npm ERR! 
npm ERR! npm ERR! A complete log of this run can be found in: /home/user/.npm/_logs/2025-11-07T19_35_23_944Z-debug-0.log

npm ERR! A complete log of this run can be found in: /home/user/.npm/_logs/2025-11-07T19_35_16_890Z-debug-0.log
npm install did not exit successfully
tidy [extra_checks]: IO error: npm install returned exit code exit status: 127
tidy [extra_checks]: FAIL
tidy: The following check failed: extra_checks
Bootstrap failed while executing `test src/tools/tidy tidyselftest --extra-checks=py,cpp,js,spellcheck`
Command `/checkout/obj/build/x86_64-unknown-linux-gnu/stage1-tools-bin/rust-tidy /checkout /checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/cargo /checkout/obj/build 4 /node/bin/npm --extra-checks=py,cpp,js,spellcheck` failed with exit code 1
Created at: src/bootstrap/src/core/build_steps/tool.rs:1549:23
Executed at: src/bootstrap/src/core/build_steps/test.rs:1279:29

Command has failed. Rerun with -v to see more details.
Build completed unsuccessfully in 0:03:10
  local time: Fri Nov  7 19:35:53 UTC 2025
  network time: Fri, 07 Nov 2025 19:35:53 GMT
##[error]Process completed with exit code 1.
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