Add long paths prerequisite to NetCore_GettingStarted.md

[carlossanlop]

Improve documentation to prevent contributors from falling into this issue: #6632 (comment)

[buyaa-n]

This is related to any build right? Maybe add into https://github.com/dotnet/roslyn-analyzers#getting-started?

[carlossanlop]

This is related to any build right? Maybe add into https://github.com/dotnet/roslyn-analyzers#getting-started?

Ah, good point. I missed those instructions.

I think it's worth having this info in both places, if that's alright with you.

[sharwell]

We should wait for dotnet/roslyn#68217 to merge and adopt the same strategy here.

[carlossanlop]

@sharwell should that roslyn PR block this docs PR though? Can you please explain?

[sharwell]

@carlossanlop I believe yes. Once the strategy from dotnet/roslyn is finalized, the documentation will be redundant because the build will perform the necessary change so the user doesn't need to. Also, the steps to enable the feature will be simplified to running a script which the error output points to.

[carlossanlop]

The roslyn PR has been merged. @sharwell should I close this?