ECR login error on Windows runner

[mr-smithers-excellent]

The ECR login command is causing an error on Windows platform runners, resulting in the following message:

##[error]Command failed: $(aws ecr get-login --region us-east-1 --no-include-email)
'$' is not recognized as an internal or external command,
operable program or batch file.

Logic will need to be added to handle this login command via PowerShell.