Failing in CI but not at desk (in C++), so add some logging sigh

Author: grynspan

Sources/Testing/Support/FileHandle.swift

@@ -738,11 +738,17 @@ let rootDirectoryPath: String = {
   if count > 0 {
     withUnsafeTemporaryAllocation(of: wchar_t.self, capacity: Int(count) + 1) { buffer in
       _ = GetSystemWindowsDirectoryW(buffer.baseAddress!, UINT(buffer.count))
+      let windowsPath = String.decodeCString(buffer.baseAddress!, as: UTF16.self)?.result
       let rStrip = PathCchStripToRoot(buffer.baseAddress!, buffer.count)
       if rStrip == S_OK || rStrip == S_FALSE {
         result = String.decodeCString(buffer.baseAddress!, as: UTF16.self)?.result
+      } else {
+        fatalError("Failed to strip Windows path '\(windowsPath)': \(rStrip)")
       }
     }
+  } else {
+    let errorCode = GetLastError()
+    fatalError("Failed to get the length of the system Windows directory path: \(errorCode)")
   }
 
   // If we weren't able to get a path, fall back to "C:\" on the assumption that