Custom plugin is not picked up when build with Mingw

Custom plugin is not being picked up when it is build with Mingw. Exact same project works without any problem with MSVS and on Linux.

it turns out that for some reason Mingw needs plugin name start with 'lib'+plugin name, qmldir file, where as MSVS can work with plugin name only.

Attached example can be used to see the issue. 

Steps
unzip and and build with MSVS it will show a button. 

Same will also work on Linux gcc

But with MingW it will end up showing Error

QQmlApplicationEngine failed to load component
qrc:/main.qml:6:1: module "myplugin" plugin "myplugin" not found

If "plugin myplugin" is changed to "plugin libmyplugin" then this works.