How can I maintain file reference integrity from a WIX Setup Library

I am using the Wix Toolset 3.8 Visual Studio add-in. I have created a WIX Setup Library which encapsulates some common components that will be consumed by various service deployment projects. This library includes references to several solution files which need to be packaged into each deployment.

These dependencies are used in my wix library fragments in a few different ways. For example:

<Binary Id="InstallationScript" SourceFile=".\Dependency1.vbs" />
<CustomAction Id="DependencyAction"
              BinaryKey="InstallationScript"
              VBScriptCall=""
              Execute="deferred"
              Return="check"
              HideTarget="no"/>
<Component Id="DLL_Component" Guid="4745D9E2-0EBA-EE57-D8DB-677ADA9E9EC8">
    <File Id="DLL1" Name="Dependency1.DLL" Source=".\Dependency1.dll" Vital="yes" KeyPath="yes" DiskId="1"/>
</Component>

The WIX Setup Library builds fine whether I add the files to the project as a link or copy them into the project directory, and whether I reference them in the project directory or use a relative path to their original location. The problem comes when I include the fragment in my WIX Setup Project for my service deployment.

<Custom Action="DependencyAction"  Before="InstallFinalize">
    NOT INSTALLED AND NOT UPGRADINGPRODUCTCODE
</Custom>

The Setup Project is not at the same relative depth in the folder structure, so a relative path does not point to the same place as it does when referenced from the WIX Library. When I reference the action or feature from the WIX library I get errors like The system cannot fine the file '.\Dependency1.dll' The XML is being read exactly as it is and referenced from the Setup Project location rather than from the Library Project location, so the relative directory is wrong. I can set the relative path in the WIX library to what it should be for the Setup Project that consumes it, or I can copy the solution files into the Setup Project directory as well, but of course, that completely defeats the purpose of using a common WIX library. There are other service deployment projects that need to consume this library.

So the question is, how do I reference solution files in a WIX library in a way that can be used by the Setup Project that consumes it, regardless of the directory that the Setup Project is in?

Create a binary .wixlib that contains the files referenced in your authoring. (That's -bf at the command line, BindFiles property in the .wixproj, "Bind files into the library file" checkbox in Votive.)