You can't do that, this is a limitation for security. (We assume only administrator can copy file to your photoshop folder.)
But, if you own the panel, you may add some script to the panel's onInit event to copy your script file to photoshop's script folder.
Or install the script file to photoshop folder manually.
You should :
1 ) configure the mxi file adding:
<file source="NameOf yourScript.jsx" destination="$scripts" file-type="ordinary" />
between the tags <files> here </files>
2) place the script file near the mxi file.
3) package the extension to create the installer.
This way the script file will be automatically placed inside photoshop script folder by the installer