wal2json: fix build for linux and skip test if root
wal2json: fix build for linux and skip test if root

Closes #16594.

Signed-off-by: Dawid Dziurla <c4a7db180859322ef5630a1dfc2805b5bc97fc25@gmail.com>

Linuxbrew/homebrew-core,maxim-belkin/homebrew-core,Linuxbrew/homebrew-core,LinuxbrewTestBot/homebrew-core,rwhogg/homebrew-core,maxim-belkin/homebrew-core,LinuxbrewTestBot/homebrew-core,rwhogg/homebrew-core