Revert "Swift SDKs: fix toolset.linker.path not passed to -ld-path (#6719)"

[neonichu]

This reverts commit d328002.

This broke existing Swift SDKs:

ld.lld: error: unable to find library -ld-path=/Users/neonacho/Library/org.swift.swiftpm/swift-sdks/5.8-RELEASE_rhel_ubi9_aarch64.artifactbundle/5.8-RELEASE_rhel_ubi9_aarch64/aarch64-unknown-linux-gnu/swift.xctoolchain/usr/bin/ld.lld 

[neonichu]

@swift-ci please smoke test

[neonichu]

@swift-ci please test

[tomerd]

@MaxDesiatov feel free to bring back once the regressions are addressed

[MaxDesiatov]

cc @kabiroberai

[kabiroberai]

Ah, the problem is that we can't directly forward -ld-path to clang anymore because the clang option uses two dashes. Should be an easy fix in swift-driver; will put up a PR and after that's merged it should be safe to revert the revert.

Update: created swiftlang/swift-driver#1447.

[tomerd]

@MaxDesiatov is there a test we can add to make sure we don't regress?

[MaxDesiatov]

Unfortunately, this would be caught only by the end-to-end test that's currently implemented in the Swift SDK generator. We'll have to spend some time coming up with some better integration tests for this, especially as they involve Clang.

[neonichu]

Maybe we can find a way to enable a cross-repo kind of workflow so that we could run the tests in Swift SDK generator against a specific PR on SwiftPM? Similar to how we can run the compatibility suite if we make larger changes to the package manifest.

[MaxDesiatov]

Yes, compatibility suite is something I definitely want, just found a regression in cross-compilation to UBI9 with Swift 5.9, which wasn't present with Swift 5.9, only present with certain packages, like swift-log 😭

[kabiroberai]

Now that swiftlang/swift-driver#1447 is merged we should be able to revert this. @neonichu will you put up a PR or shall I?