Work around MCG bug around ref char marshalling (dotnet/corert#5481)

The change in the P/invoke signature that came from CoreCLR triggers a bug in MCG on the TFS side.

Signed-off-by: dotnet-bot <dotnet-bot@microsoft.com>
Signed-off-by: dotnet-bot-corefx-mirror <dotnet-bot@microsoft.com>

Author: MichalStrehovsky

src/Common/src/CoreLib/Interop/Windows/Kernel32/Interop.GetFullPathNameW.cs

@@ -13,6 +13,17 @@ internal partial class Kernel32
         /// WARNING: This method does not implicitly handle long paths. Use GetFullPathName or PathHelper.
         /// </summary>
         [DllImport(Libraries.Kernel32, SetLastError = true, CharSet = CharSet.Unicode, BestFitMapping = false, ExactSpelling = true)]
+#if PROJECTN
+        internal static extern unsafe uint GetFullPathNameW(string path, uint numBufferChars, char* buffer, IntPtr mustBeZero);
+
+        // Works around https://devdiv.visualstudio.com/web/wi.aspx?pcguid=011b8bdf-6d56-4f87-be0d-0092136884d9&id=575202
+        internal static unsafe uint GetFullPathNameW(string path, uint numBufferChars, ref char buffer, IntPtr mustBeZero)
+        {
+            fixed (char* pBuffer = &buffer)
+                return GetFullPathNameW(path, numBufferChars, pBuffer, mustBeZero);
+        }
+#else
         internal static extern uint GetFullPathNameW(string path, uint numBufferChars, ref char buffer, IntPtr mustBeZero);
+#endif
     }
 }

src/Common/src/CoreLib/Interop/Windows/Kernel32/Interop.GetLongPathNameW.cs

@@ -13,6 +13,17 @@ internal partial class Kernel32
         /// WARNING: This method does not implicitly handle long paths. Use GetFullPath/PathHelper.
         /// </summary>
         [DllImport(Libraries.Kernel32, SetLastError = true, CharSet = CharSet.Unicode, BestFitMapping = false, ExactSpelling = true)]
+#if PROJECTN
+        internal static extern unsafe uint GetLongPathNameW(ref char lpszShortPath, char* lpszLongPath, uint cchBuffer);
+
+        // Works around https://devdiv.visualstudio.com/web/wi.aspx?pcguid=011b8bdf-6d56-4f87-be0d-0092136884d9&id=575202
+        internal static unsafe uint GetLongPathNameW(ref char lpszShortPath, ref char lpszLongPath, uint cchBuffer)
+        {
+            fixed (char* plpszLongPath = &lpszLongPath)
+                return GetLongPathNameW(ref lpszShortPath, plpszLongPath, cchBuffer);
+        }
+#else
         internal static extern uint GetLongPathNameW(ref char lpszShortPath, ref char lpszLongPath, uint cchBuffer);
+#endif
     }
 }