apertis-abi-compare: general improvements

General improvements for apertis-abi-compare:

• rename detect_libname to detect_libnames (was partially renamed in the previous version)
• run 'apt update' before 'apt install' to be sure having the latest versions
• run 'apt install' with '-y' argument because noninteractive call
• force flushing for stdout to avoid mixed ordering of stdout and stderr outputs

https://phabricator.apertis.org/T8626

Signed-off-by: Dylan Aïssi dylan.aissi@collabora.com