[Path] Set FD to -1 in moved-from TempFile

When moving a temp file, explicitly set the file descriptor to -1 so we
can never accidentally close the moved-from TempFile.

Differential revision: https://reviews.llvm.org/D63087

llvm-svn: 363083
diff --git a/llvm/lib/Support/Path.cpp b/llvm/lib/Support/Path.cpp
index 5312e1d..c492601 100644
--- a/llvm/lib/Support/Path.cpp
+++ b/llvm/lib/Support/Path.cpp
@@ -1125,6 +1125,7 @@
   TmpName = std::move(Other.TmpName);
   FD = Other.FD;
   Other.Done = true;
+  Other.FD = -1;
   return *this;
 }