More missing header inclusions from llvm_unreachable migration.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@140369 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Driver/Phases.cpp b/lib/Driver/Phases.cpp
index d7f6ab9..c465e1d 100644
--- a/lib/Driver/Phases.cpp
+++ b/lib/Driver/Phases.cpp
@@ -8,6 +8,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "clang/Driver/Phases.h"
+#include "llvm/Support/ErrorHandling.h"
 
 #include <cassert>