#1163 Build fails if Wixlib reference is an UNC path

[ptam]

We are using a custom UI wixlib that is located in a network share. The library is referenced from the project using a property that holds an UNC path to server directory, for example:

<propertygroup>
<repositorydir>\Server\share\</repositorydir>
</propertygroup>
<wixlibrary include="$(RepositoryDir)UILib\UI.wixlib">
<hintpath>$(RepositoryDir)UILib\UI.wixlib</hintpath>
</wixlibrary>

When building the project, MSBuild passes the path to light in correct format including both backslashes in the path (\..), but the code in wconsole.dll that parses command line arguments skips one backslash of the path causing light to receive the path as "\Server\share\UI.wixlib" and the build fails. This issue has been there from version 3725.

[ptam]

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Correction tested and verified with WIX 3.0.4318