runtime sourcelink file missing with latest sourcelink version

[MichaelSimons]

The darc dependency flow PR into installer is failing to build runtime in source build with the following error:

/vmr/src/runtime/artifacts/source-build/self/src/eng/versioning.targets(194,5): error MSB3030: Could not copy the file "/vmr/src/runtime/artifacts/source-build/self/src/artifacts/obj/coreclr/runtime-prereqs/x64/Release/runtime-prereqs.sourcelink.json" because it was not found. [/vmr/src/runtime/artifacts/source-build/self/src/src/coreclr/runtime-prereqs.proj]

This appears to be released to the changes made in #989. cc @tmat

The _GenerateSourceLinkFile task is not writing the runtime-prereqs.sourcelink.json file.

binglog: https://artprodcus3.artifacts.visualstudio.com/A6fcc92e5-73a7-4f88-8d13-d9045b45fb27/cbb18261-c48f-4abb-8651-8cdcb5474649/_apis/artifact/cGlwZWxpbmVhcnRpZmFjdDovL2RuY2VuZy1wdWJsaWMvcHJvamVjdElkL2NiYjE4MjYxLWM0OGYtNGFiYi04NjUxLThjZGNiNTQ3NDY0OS9idWlsZElkLzIzMjE1NS9hcnRpZmFjdE5hbWUvQ2VudE9TU3RyZWFtOF9PbmxpbmVfTXNmdFNka194NjRfQnVpbGRMb2dzX0F0dGVtcHQx0/content?format=file&subPath=%2Fsrc%2Fruntime%2Fartifacts%2Fsource-build%2Fself%2Fsrc%2Fartifacts%2Fsourcebuild.binlog

[MichaelSimons]

The sourcelink PR intends to avoid writing the json file in certain situations. Is this runtime situation one of those or not? If it is, then it seems there is downstream targets that need updating react to the json file not being created.

[tmat]

The change doesn't write the file instead of writing a file that has empty mapping. This is necessary for bundling Source Link to SDK.

[MichaelSimons]

The change doesn't write the file instead of writing a file that has empty mapping. This is necessary for bundling Source Link to SDK.

I'm not following. Are you saying a change is needed in Runtime to react to this change or is there something wrong in source link for this usage scenario?

[tmat]

Actually, might be a bug in Source Link. I updated the task to log message when it decides not to write the file that includes the reason. The binlog doesn't show the message, so maybe it's not using the latest version yet. Would be good to see binlog using the latest version.

Odd, I see _GenerateSourceLinkFile target invoked multiple times with the same output path. The first writes the file, the second does not, presumably because it already has the right content.

[tmat]

Oh, here is the issue:

[tmat]

Ok, I think this is a bug in sourcelink target