simplify check_cfg_arg impl

[hkBst]

No description provided.

[rustbot]

Some changes occurred in cfg and check-cfg configuration

cc @Urgau

[rustbot]

r? @Mark-Simulacrum

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[rust-log-analyzer]

The job aarch64-gnu-llvm-20-2 failed! Check out the build log: (web) (plain enhanced) (plain)

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

[RUSTC-TIMING] object test:false 0.743
error[E0308]: mismatched types
   --> src/bootstrap/src/utils/helpers/tests.rs:50:43
    |
 50 |     assert_eq!(check_cfg_arg("bootstrap", None), "--check-cfg=cfg(bootstrap)");
    |                -------------              ^^^^ expected `&[&str]`, found `Option<_>`
    |                |
    |                arguments to this function are incorrect
    |
    = note: expected reference `&[&str]`
                    found enum `std::option::Option<_>`
note: function defined here
   --> src/bootstrap/src/utils/helpers.rs:494:8
    |
494 | pub fn check_cfg_arg(name: &str, values: &[&str]) -> String {
    |        ^^^^^^^^^^^^^             ---------------

error[E0308]: mismatched types
   --> src/bootstrap/src/utils/helpers/tests.rs:52:38
    |
 52 |         check_cfg_arg("target_arch", Some(&["s360"])),
    |         -------------                ^^^^^^^^^^^^^^^ expected `&[&str]`, found `Option<&[&str; 1]>`
    |         |
    |         arguments to this function are incorrect
    |
    = note: expected reference `&[&str]`
                    found enum `std::option::Option<&[&str; 1]>`
note: function defined here
   --> src/bootstrap/src/utils/helpers.rs:494:8
    |
494 | pub fn check_cfg_arg(name: &str, values: &[&str]) -> String {
    |        ^^^^^^^^^^^^^             ---------------

error[E0308]: mismatched types
   --> src/bootstrap/src/utils/helpers/tests.rs:56:36
    |
 56 |         check_cfg_arg("target_os", Some(&["nixos", "nix2"])),
    |         -------------              ^^^^^^^^^^^^^^^^^^^^^^^^ expected `&[&str]`, found `Option<&[&str; 2]>`
    |         |
    |         arguments to this function are incorrect
    |
    = note: expected reference `&[&str]`
                    found enum `std::option::Option<&[&str; 2]>`
note: function defined here
   --> src/bootstrap/src/utils/helpers.rs:494:8
    |
494 | pub fn check_cfg_arg(name: &str, values: &[&str]) -> String {
    |        ^^^^^^^^^^^^^             ---------------

For more information about this error, try `rustc --explain E0308`.
[RUSTC-TIMING] bootstrap test:true 3.608
error: could not compile `bootstrap` (lib test) due to 3 previous errors

[Urgau]

r? Urgau