Can someone explain how glfw3.dll gets created?

[WhatMeWorry via Digitalmars-d-learn]

I have a simple GLFW3 program running in Visual D integrated 
shell, that kept aborting at DerelictFLFW3.load() with a "failed 
to load the shared libraries: glfw3.dll.'

So I found a glfw3.dll somewhere and moved it into the project 
folder (I know this is bad technique) and that fixed the problem.

But now I'm wondering were this glfw3.dll came from.

I rebuildt the DerelictGLFW3 with dub as per the instructions.

E:\DerelictGLFW3-master>dub build
Building derelict-glfw3 ~master configuration "library", build 
type debug.
Running dmd...

And I see
E:\DerelictGLFW3-master\source\derelict\glfw3\glfw3.d  which is 
used for compile time.

And the
E:\DerelictGLFW3-master\lib\DerelictGLFW3.lib which is the static 
library required at link time.

But I couldn't find any glfw3.dll under the 
E:\DerelictGLFW3-master path.


I did however, find these lines in the DerelictGLFW3/glfw3.d code:
...
static if( Derelict_OS_Windows )
    enum libNames = "glfw3.dll";
. . .
class DerelictGLFW3Loader : SharedLibLoader {
     public this() {
         super( libNames );
     }

     protected override void loadSymbols() {
         bindFunc( cast( void** )&glfwInit, "glfwInit" );
         bindFunc( cast( void** )&glfwTerminate, "glfwTerminate" );
         bindFunc( cast( void** )&glfwGetVersion, "glfwGetVersion" 
);
         bindFunc( cast( void** )&glfwGetVersionString, 
"glfwGetVersionString" );
         bindFunc( cast( void** )&glfwSetErrorCallback, 
"glfwSetErrorCallback" );
  ...

But I don't believe this will create the glfw3.dll file?  If I'm 
correct, how, when and where is glfw3.dll created.

thanks as always.