LineEndingCheck: bugfix: Fails if not run from workspace root (#540)

## Description

LineEndingCheck would fail if `stuart_ci_build` was not run from the
workspace root because of two separate locations that used "." for the
workspace root rather than the true workspace root. This commit updates
it to use the true workspace root rather than ".".

- [ ] Impacts functionality?
- **Functionality** - Does the change ultimately impact how firmware
functions?
- Examples: Add a new library, publish a new PPI, update an algorithm,
...
- [ ] Impacts security?
- **Security** - Does the change have a direct security impact on an
application,
    flow, or firmware?
  - Examples: Crypto algorithm change, buffer overflow fix, parameter
    validation improvement, ...
- [ ] Breaking change?
- **Breaking change** - Will anyone consuming this change experience a
break
    in build or boot behavior?
- Examples: Add a new library class, move a module to a different repo,
call
    a function in a new library class in a pre-existing module, ...
- [ ] Includes tests?
  - **Tests** - Does the change include any explicit test code?
  - Examples: Unit tests, integration tests, robot tests, ...
- [ ] Includes documentation?
- **Documentation** - Does the change contain explicit documentation
additions
    outside direct code modifications (and comments)?
- Examples: Update readme file, add feature readme file, link to
documentation
    on an a separate Web page, ...

## How This Was Tested

CI

## Integration Instructions

N/A

.pytool/Plugin/LineEndingCheck/LineEndingCheck.py

@@ -91,7 +91,7 @@ def GetTestName(self, packagename: str, environment: VarDict) -> Tuple:
     #   function to check and warn if git config reports that
     #   autocrlf is configured to TRUE
     def _check_autocrlf(self):
-        r = Repo(".")
+        r = Repo(self._abs_workspace_path)
         try:
             result = r.config_reader().get_value("core", "autocrlf")
             if result:
@@ -250,9 +250,8 @@ def RunBuildPlugin(self, package_rel_path: str, edk2_path: Edk2Path,
           0  : Ran successfully
           -1 : Skipped due to a missing pre-requisite
         """
+        self._abs_workspace_path = edk2_path.WorkspacePath
         self._check_autocrlf()
-        self._abs_workspace_path = \
-            edk2_path.GetAbsolutePathOnThisSystemFromEdk2RelativePath('.')
         self._abs_pkg_path = \
             edk2_path.GetAbsolutePathOnThisSystemFromEdk2RelativePath(
                         package_rel_path)