[ubuntu] Unify approach to /etc/environment (#8904)

* [ubuntu] Unify approach to /etc/environment

* [ubuntu] fix typo in XDG_CONFIG_HOME name

images/ubuntu/scripts/build/configure-environment.sh

@@ -6,17 +6,18 @@
 
 # Source the helpers for use with the script
 source $HELPER_SCRIPTS/os.sh
+source $HELPER_SCRIPTS/etc-environment.sh
 
 # Set ImageVersion and ImageOS env variables
-echo ImageVersion=$IMAGE_VERSION | tee -a /etc/environment
-echo ImageOS=$IMAGE_OS | tee -a /etc/environment
+setEtcEnvironmentVariable "ImageVersion" "${IMAGE_VERSION}"
+setEtcEnvironmentVariable "ImageOS" "${IMAGE_OS}"
 
 # Set the ACCEPT_EULA variable to Y value to confirm your acceptance of the End-User Licensing Agreement
-echo ACCEPT_EULA=Y | tee -a /etc/environment
+setEtcEnvironmentVariable "ACCEPT_EULA" "Y"
 
 # This directory is supposed to be created in $HOME and owned by user(https://github.com/actions/runner-images/issues/491)
 mkdir -p /etc/skel/.config/configstore
-echo 'XDG_CONFIG_HOME=$HOME/.config' | tee -a /etc/environment
+setEtcEnvironmentVariable "XDG_CONFIG_HOME" '$HOME/.config'
 
 # Change waagent entries to use /mnt for swapfile
 sed -i 's/ResourceDisk.Format=n/ResourceDisk.Format=y/g' /etc/waagent.conf
@@ -29,7 +30,7 @@ sed -i 's/::1 ip6-localhost ip6-loopback/::1     localhost ip6-localhost ip6-loo
 # Prepare directory and env variable for toolcache
 AGENT_TOOLSDIRECTORY=/opt/hostedtoolcache
 mkdir $AGENT_TOOLSDIRECTORY
-echo "AGENT_TOOLSDIRECTORY=$AGENT_TOOLSDIRECTORY" | tee -a /etc/environment
+setEtcEnvironmentVariable "AGENT_TOOLSDIRECTORY" "${AGENT_TOOLSDIRECTORY}"
 chmod -R 777 $AGENT_TOOLSDIRECTORY
 
 # https://www.elastic.co/guide/en/elasticsearch/reference/current/vm-max-map-count.html