Methods from classes exported from another library have invalid links

[sethladd]

• Generate the docs for test_package
• View test_package/doc/api/ex/DateTime/toUtc.html
• The link for DateTime in the main display of the signature of the method is invalid.

Actual: file:///Users/sethladd/Code/dartdoc/test_package/doc/api/dart-core/DateTime-class.html

Expected: file:///Users/sethladd/Code/dartdoc/test_package/doc/api/ex/DateTime-class.html