Mirrored Objects and Normals

Hi. I have two objects (A) and (B). (B) was created by selecting object (A) and ALT + D , so they are both using the same mesh. Then I mirrored that object on global Y axis. The problem is after I export from Blender to Substance painter (or other programs) then the mirrored object (B) has its normals flipped out.

Is there any way to retain using the same mesh for all objects and having the normals facing the correct way ?
The end line for the models is Unity and I wanted to take advantage of using the same mesh for multiple objects.

Don’t use Blender instancing in this case and instead rely on the same texture.
Blender instancing makes sense only in Blender. Once it’s exported it is real geometry. In your case as one of objects was mirrored in Object mode it had negative scale which upon export results in inverted normals. It is impossible to apply scale in Blender for instanced object since object has multiple users.
If you want to optimize resources build one texture which will be used for 2 different objects.