Windows PowerShell:
(Get-ItemProperty -Path ’HKLM:\SOFTWARE\Microsoft\Windows NT\CurrentVersion’ -Name BuildLab).BuildLab

14955.rs_prerelease.161020-1700

(Get-ItemProperty -Path ’HKLM:\SOFTWARE\Microsoft\Windows NT\CurrentVersion’ -Name BuildLabEx).BuildLabEx

14955.1000.amd64fre.rs_prerelease.161020-1700

Bash on Ubuntu on Windows:
/mnt/c/Windows/System32/WindowsPowerShell/v1.0/powershell.exe -command ”(Get-ItemProperty -Path ’HKLM:\SOFTWARE\Microsoft\Windows NT\CurrentVersion’ -Name BuildLabEx).BuildLabEx”

14955.1000.amd64fre.rs_prerelease.161020-1700