Do not add x86 host to PATH on 64-bit machines

[NikolaMilosavljevic]

This fixes the remaining issue with non-native host paths in machine's environment (PATH).

The fix uses a different model than x64-on-arm64. It is a simpler change as it's easy to determine if machine is 64-bit, using WersionNT64 property. This solution avoids unnecessary changes in arcade infra and adding additional complexity.

[joeloff]

We should document this change so that users that only install the x86 SDK on a 64-bit OS manually update the PATH variable.

[NikolaMilosavljevic]

We should document this change so that users that only install the x86 SDK on a 64-bit OS manually update the PATH variable.

Yes, this needs to be documented as a breaking change. @richlander is there any guidance for publishing BCNs? I could help with that, unless there is an established process and team, to which I should defer this.

[richlander]

https://github.com/dotnet/runtime/blob/main/docs/project/breaking-change-process.md

[NikolaMilosavljevic]

BCN issue: #70039

[ghost]

Added needs-breaking-change-doc-created label because this PR has the breaking-change label.

When you commit this breaking change:

1. Create and link to this PR and the issue a matching issue in the dotnet/docs repo using the breaking change documentation template, then remove this needs-breaking-change-doc-created label.
2. Ask a committer to mail the .NET Breaking Change Notification DL.

Tagging @dotnet/compat for awareness of the breaking change.

[NikolaMilosavljevic]

/backport to release/6.0

[github-actions]

Started backporting to release/6.0: https://github.com/dotnet/runtime/actions/runs/2450031373