build_tools: Fix Windows assertion when path contains ellipses

A path of "$(SRCROOT)/../../SomeFile.cpp" would lose the fake C:\ prefix
when the ellipses are collapsed, and trigger a non-absolute File
assertion.

extras/Build/juce_build_tools/utils/juce_RelativePath.h

@@ -107,21 +107,12 @@ namespace juce::build_tools
 
         File getFakeFile() const
         {
-           #if JUCE_WINDOWS
-            if (isAbsolutePath (path))
-            {
-                // This is a hack to convert unix-style absolute paths into valid absolute Windows paths to avoid hitting
-                // an assertion in File::parseAbsolutePath().
-                if (path.startsWithChar (L'/') || path.startsWithChar (L'$') || path.startsWithChar (L'~'))
-                    return File (String ("C:\\") + windowsStylePath (path.substring (1)));
-
-                return File (path);
-            }
-           #endif
+            const auto unixStylePath = toUnixStyle();
+            const auto name = unixStylePath.substring (unixStylePath.lastIndexOfChar ('/') + 1);
 
             // This method gets called very often, so we'll cache this directory.
             static const File currentWorkingDirectory (File::getCurrentWorkingDirectory());
-            return currentWorkingDirectory.getChildFile (path);
+            return currentWorkingDirectory.getChildFile (name);
         }
     };