Unity locks dll libraries (even after deleting from editor)

Hi,

I use some native dll's in my project - I setup my C++ library project so that the library gets copied after build into Unity Assets folder....

problem is that Unity locks this file after loading and therefore it cannot be rebuilt again from my C++ project.

Is there a way around this? Even when I delete the file via Unity editor, it is still locked in the file system.

Thanks!