[Build] Skip early swift driver/syntax

[bnbarham]

CI currently skips these because there is no host Swift anyway. Forcefully skip them to allow using the release docker images as the base image (with Clang and Swift pre-installed). CentOS 7 needs this as the packaged Clang (in software collections) is only Clang 5. It does technically support C++17 but has a bug causing a compiler error for most uses of variant (now used all throughout LLVM) - llvm/llvm-project#32569.

This is temporary as the bootstrap should work. It currently fails when linking libswiftDemangle.so, which tries to link with swiftCore, but fails to find it. Need to look into that, but this is an easy fix that doesn't regress anything for now.

[bnbarham]

@swift-ci please test

[compnerd]

I think that this is fine, but please get @shahmishal to sign off on this before merging.

[etcwilde]

LGTM. Just wanted to make sure that we actually want to make this change for all the Linux bots though. Would it be better to have a specific configuration for this since it’s a special case to work around the old toolchain?

[bnbarham]

LGTM. Just wanted to make sure that we actually want to make this change for all the Linux bots though. Would it be better to have a specific configuration for this since it’s a special case to work around the old toolchain?

We're changing all the Linux images to use the release image instead, which we need to do for bootstrapping regardless. It's just that the main reason for doing this now is for CentOS 😅

But it being broken would be an issue on all of them, not just CentOS.

[bnbarham]

@swift-ci please smoke test macOS platform

[bnbarham]

Turns out we may not actually need this. It looks like there is in fact a llvm-toolset-7.0 package that includes Clang 7 (note the 7.0 as opposed to llvm-toolset-7). In that case it's probably better for us to fix the bootstrap before updating the packages to use the release image, which means we wouldn't need this patch at all.