"localhost" and hostname resolution on hosts with no systemd-resolved

Context

Flatpak containers currently do not resolve localhost and hostname on hosts that don't use systemd-resolved and have no relevant entries in /etc/hosts.

Description

Runtime's nsswitch.conf is set to:

hosts: files resolve [!UNAVAIL=return] dns

Adding nss-myhostname into the runtime and configuring nsswitch.conf to use it should fix this problem:

hosts: files myhostname resolve [!UNAVAIL=return] dns

Acceptance Criteria

$ flatpak run --command=getent org.freedesktop.Platform ahosts localhost
::1             STREAM localhost
::1             DGRAM  
::1             RAW    
127.0.0.1       STREAM 
127.0.0.1       DGRAM  
127.0.0.1       RAW
Edited by dos