Custom Build: custom AMD name doesn't work

[jens.simon80@…]

When doing a custom build using a different AMD module name like

grunt custom --amd=""

or

grunt custom --amd="customname"

the

define('exports/amd',[
	"../core"
], function( jQuery ) {

won't be removed. This means that when used with RequireJS

define(['customname'], function (jQuery) {
    // ...
});

doesn't return the jQuery object because it defines always the name "exports/amd" for the module.

[Timmy Willison]

Build: Fix AMD option for custom builds

Fixes #14859

Changeset: 984f77a930aa322bcc277762303370d7a2a4667a