Cargo -Z extra-link-arg= issues a warning

[berkus]

Problem

Related to #9426

I need to pass extra-link-args on command line from the makefile, but now cargo issues a warning

warning: flag `-Z extra-link-arg` has been stabilized in the 1.56 release, and is no longer necessary
  Additional linker arguments are now supported without passing this flag.

Does it mean I can now pass linker flags directly on the command line like --script=link.ld?

Steps

Parent Makefile.toml:

[env]
# This is passed to cargo if LINK_SCRIPT is set in sub-makefile
LINK_ARG = "-Z extra-link-arg=--script=${LINK_SCRIPT}"

Makefile.toml

[env]
# This script is specific per-project-binary.
# I do not use, neither need to use build.rs here.
LINK_SCRIPT = "bin/microboot/src/link.ld"

[tasks.build]
env = { "TARGET_FEATURES" = "" }
args = ["build", "--target=${TARGET_JSON}", "@@split(STD, )", "@@split(LINK_ARG, )", "--release", "--features=${TARGET_FEATURES}"]

Which gives a command line like

[cargo-make][1] INFO - Execute Command: "cargo" "build" "--target=/Metta/vesper/targets/aarch64-vesper-metta.json" "-Z" "build-std=compiler_builtins,core,alloc" "-Z" "build-std-features=compiler-builtins-mem" "-Z" "extra-link-arg=--script=linker/aarch64.ld" "--release" "--features="

Possible Solution(s)

1. not issue the warning if -Z extra-link-arg will continue to work
2. provide an alternative way to specify link-arg on command line if the above flag will be removed.

Notes

No response

Version

❯ cargo version --verbose
cargo 1.58.0-nightly (94ca096af 2021-10-29)
release: 1.58.0
commit-hash: 94ca096afbf25f670e76e07dca754fcfe27134be
commit-date: 2021-10-29
host: aarch64-apple-darwin
libgit2: 1.3.0 (sys:0.13.23 vendored)
libcurl: 7.77.0 (sys:0.4.49+curl-7.79.1 system ssl:(SecureTransport) LibreSSL/2.8.3)
os: Mac OS 12.0.1 [64-bit]

[ehuss]

Maybe I'm a bit confused by the question, but -Zextra-link-arg never took arguments itself. It just enabled adding linker arguments via build scripts. There is more documentation on how that works at https://doc.rust-lang.org/cargo/reference/build-scripts.html#outputs-of-the-build-script (the cargo:rustc-link-arg instructions). Build scripts may now output those instructions without -Zextra-link-arg.

[berkus]

Ahh, that's fine then, thanks!

Let's pivot a bit: What about providing a linker script path directly from cargo invocation, how is it possible if at all?

[berkus]

On the other hand, build.rs files seem to work fine for this task.