How would I change the icon of Qt project targeted for android so that the launcher of application has this icon?
You should create an Android manifest file and edit it in Qt Creator. Go to Projects > Build Android APK > Details
Now Select Create Templates to create the manifest file and to open it in editor :
As shown in the picture, you can set three versions of icons for your application with low, medium, and high DPI values, from left to right.
This new way of making an android manifest file is available since Qt 5.4 along Qt Creator 3.3. There used to be a Create AndroidManifest.xml button in Projects->Run->Deploy in previous versions.