network share path fails to find files

**Operation System**: Windows

**DocFX Version Used**: Version 2.40.12

**Template used**: custom template

**Steps to Reproduce**:

1. Set a content file path to a network path

**Expected Behavior**:
Like the `dest` property,I would expect that the file path, even if glob based would work and find files.

**Actual Behavior**:
:D it doesn't find the files. `dest` seems to work no issue, but it is clear that it is rooting from the highlighted local path. I have tried it out with different configs, but they all error or just don't find anything.



**ISSUE AT**
Seems that the issue is from [here ](https://github.com/dotnet/docfx/blob/ffb02059c0d4fa983afce1d3876b02b77f017f47/src/Microsoft.DocAsCode.Build.Engine/FileCollection.cs#L46) As it is goign to force it down
```
var rootedBaseDir = Path.Combine(DefaultBaseDir, baseDir ?? string.Empty);
```