Change operation_not_supported to not_supported.

Apparently operation_not_supported is...  not supported everywhere.

llvm-svn: 268348
diff --git a/llvm/lib/DebugInfo/PDB/Raw/MappedBlockStream.cpp b/llvm/lib/DebugInfo/PDB/Raw/MappedBlockStream.cpp
index 25c28e5..81e75d7 100644
--- a/llvm/lib/DebugInfo/PDB/Raw/MappedBlockStream.cpp
+++ b/llvm/lib/DebugInfo/PDB/Raw/MappedBlockStream.cpp
@@ -55,5 +55,5 @@
 std::error_code MappedBlockStream::getArrayRef(uint32_t Offset,
                                                ArrayRef<uint8_t> &Buffer,
                                                uint32_t Length) const {
-  return std::make_error_code(std::errc::operation_not_supported);
+  return std::make_error_code(std::errc::not_supported);
 }