Class inheritance generated properly only when nuget packages can be resolved and code is compiled as binary as well

**Operation System**: Windows

**DocFX Version Used**: 2.50.0.0

**Template used**: default

**Steps to Reproduce**:

1. Create AbstractApi in namespace1 (dotnetcore3.1 project A)
2. Create ConfigurationApi in namespace2 (dotnetcore3.1 project B)
3. docfx init -q
4. Copy source in src/
5a. run docfx docfx,json --serve without compiled code in the ./src folder
5b. run docfx docfx,json --serve with compiled code in the ./src folder

**Expected Behavior**:

The inheritance tree on ConfigurationApi should render properly

**Actual Behavior**:

When running docfx **without** compiled code.

The inheritance tree is not rendered properly
System.Object > ConfigurationApi


When running docfx **with** compiled code.

The inheritance tree is rendered properly
System.Object > AbstractApi > ConfigurationApi