Move the error handling functions to Error.h. NFC.

llvm-svn: 244216
diff --git a/lld/ELF/DriverUtils.cpp b/lld/ELF/DriverUtils.cpp
index 7bc6fc5..a08a8bd 100644
--- a/lld/ELF/DriverUtils.cpp
+++ b/lld/ELF/DriverUtils.cpp
@@ -14,6 +14,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "Driver.h"
+#include "Error.h"
 #include "llvm/ADT/STLExtras.h"
 
 using namespace llvm;