What is the file that causes Avast to trigger alarm - is it Editor, acwin.exe or compiled game exe? When does it alarms - when you compiled it, or run ready game?
Have you tried to send false positive report to Avast company, and if yes, did they say anything?
One of the possible reasons antiviruses do not like AGS games is that they have game data appended to exe, and also being read from there during the game. I recall someone experienced the issue once that AV slowed AGS game down because it was reading sounds from its own exe, and AV probably thought that's suspicious.
A simple test may display if that is the case. If you take acwin.exe from the Editor's program files, and distribute not your compiled game exe, but acwin.exe + YourGameName.ags raw data file found in Compiled folder (since AGS 3.4.0). If it is all because of data appended to exe, then antivirus should not complain.
Obvious solution is to add an option to put all the data into separate file(s) when compiling game. Editor already does that for Linux version.