Bug#952881: [live-build] binary_iso using wrong echo helper

[jnqnfe@gmail.com]

Package: live-build
Version: 1:20191221
Owner: jnqnfe@gmail.com
Severity: minor

Echo_message() should be used instead of Echo() for "No EFI boot code
to include in the ISO".

patch to be submitted via salsa shortly (will amend commit with bug
number first)