Use error_code instead of std::string* for MemoryBuffer.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@121378 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/tools/driver/cc1as_main.cpp b/tools/driver/cc1as_main.cpp
index a0901fd..40ee20e 100644
--- a/tools/driver/cc1as_main.cpp
+++ b/tools/driver/cc1as_main.cpp
@@ -42,6 +42,7 @@
 #include "llvm/Support/Host.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/Signals.h"
+#include "llvm/Support/system_error.h"
 #include "llvm/Target/TargetAsmBackend.h"
 #include "llvm/Target/TargetAsmParser.h"
 #include "llvm/Target/TargetData.h"
@@ -224,8 +225,10 @@
     return false;
   }
 
-  MemoryBuffer *Buffer = MemoryBuffer::getFileOrSTDIN(Opts.InputFile, &Error);
+  error_code ec;
+  MemoryBuffer *Buffer = MemoryBuffer::getFileOrSTDIN(Opts.InputFile, ec);
   if (Buffer == 0) {
+    Error = ec.message();
     Diags.Report(diag::err_fe_error_reading) << Opts.InputFile;
     return false;
   }