[release/6.0] Build .rpm packages for linux arm64 (#40504)

* [release/6.0] Build .rpm packages for linux arm64

* Update Build.props

* Update Directory.Build.props

* Update Directory.Build.targets

* Update Rpm.Runtime.rpmproj

* Update Rpm.TargetingPack.rpmproj

* Avoid duplicate targeting-pack RPM Build
- if an RPM containing platform-neutral executables is platform-neutral, this should be enough

* !fixup! Change Linux ARM64 job, not ARM one

* Correct RPM arch name, include in targeting pack

* Revert "Avoid duplicate targeting-pack RPM Build"

This reverts commit 7bebff5b

* Rename x64 RPM to "x64"

Co-authored-by: Doug Bunting <6431421+dougbu@users.noreply.github.com>