Use proper string comparison for directory root to capture relative paths

[mruxmohan4]

For directory roots that differ in casing (ex: C:\\ vs c:\\), absolute instead of relative paths will appear in the solution. This change addresses that by adding a string comparison and checking the path root (drive) for the absolute root path against the folder's path root before determining whether to emit a warning (note: this will limit the scenarios where a warning is emitted).

This should help with cases where absolute paths are seen instead of relative paths, for example:
Project("{<guid>}") = "tests", "C:\projects\slngen-test\src\core\App1\tests", "{<guid>}"

Should now become:
Project("{<guid>}") = "tests", "src\core\App1\tests", "{<guid>}"

Addresses #578