Fixes unreachable on invalid cfg attribute arg. #21687

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Job	Run time
build-forc-doc-sway-lib-std	2m 8s
build-mdbook	7m 23s
build-forc-test-project	3m 59s
build-reference-examples	1m 18s
build-sway-examples	1m 32s
build-sway-lib-core	1m 7s
build-sway-lib-std	1m 16s
cargo-build-workspace	2m 20s
cargo-clippy	1m 2s
cargo-run-e2e-test-evm	6m 21s
cargo-fmt-check	14s
cargo-run-e2e-test-midenvm	6m 42s
cargo-test-forc	2m 57s
cargo-test-lib-std	5m 37s
cargo-test-sway-lsp	5m 50s
cargo-test-workspace	7m 8s
cargo-toml-fmt-check	14s
check-sdk-harness-test-suite-compatibility	39s
forc-fmt-check-panic	2m 14s
cargo-unused-deps-check	4m 19s
forc-fmt-check-sway-lib-core	1m 10s
forc-fmt-check-sway-examples	56s
forc-fmt-check-sway-lib-std	1m 7s
forc-pkg-fuels-deps-check	16s
forc-run-benchmarks	3m 41s
forc-unit-tests	2m 14s
get-fuel-core-version	49s
pre-publish-check	0s
cargo-run-e2e-test-release	15m 4s
cargo-test-forc-debug	4m 2s
cargo-test-forc-client	4m 37s
cargo-run-e2e-test	14m 59s
notify-slack-on-failure	2s
build-publish-master-image	0s
publish	0s
build-publish-release-image	0s
Build and upload forc binaries to release	0s
	1h 53m 17s

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