draco: StdioFileReader/Writer gcc 4.9/clang < 4 compatibility fix.

Fixes https://github.com/google/draco/issues/582

CMakeLists.txt

@@ -58,9 +58,12 @@ option(BUILD_FOR_GLTF "" OFF)
 option(BUILD_MAYA_PLUGIN "Build plugin library for Maya." OFF)
 option(BUILD_USD_PLUGIN "Build plugin library for USD." OFF)
 
-if(${CMAKE_CXX_COMPILER_ID} MATCHES GNU
+if((${CMAKE_CXX_COMPILER_ID} STREQUAL "GNU"
    AND ${CMAKE_CXX_COMPILER_VERSION} VERSION_LESS 5)
-  message(WARNING "GNU/GCC VERSION LESS THAN 5, ENABLING COMPATIBILITY MODE.")
+   OR (${CMAKE_CXX_COMPILER_ID} STREQUAL "Clang"
+   AND ${CMAKE_CXX_COMPILER_VERSION} VERSION_LESS 4))
+  message(WARNING
+          "GNU/GCC < v5 or Clang/LLVM < v4, ENABLING COMPATIBILITY MODE.")
   draco_enable_feature(FEATURE "DRACO_OLD_GCC")
 endif()
 

src/draco/io/stdio_file_reader.cc

@@ -11,6 +11,7 @@
 #include <io.h>
 #endif
 
+#include "draco/draco_features.h"
 #include "draco/io/file_reader_factory.h"
 
 namespace draco {
@@ -46,7 +47,11 @@ std::unique_ptr<FileReaderInterface> StdioFileReader::Open(
     return nullptr;
   }
 
+#ifndef DRACO_OLD_GCC
   return file;
+#else
+  return std::move(file);
+#endif
 }
 
 bool StdioFileReader::ReadFileToBuffer(std::vector<char> *buffer) {

src/draco/io/stdio_file_writer.cc

@@ -6,6 +6,7 @@
 #include <memory>
 #include <string>
 
+#include "draco/draco_features.h"
 #include "draco/io/file_writer_factory.h"
 
 namespace draco {
@@ -41,7 +42,11 @@ std::unique_ptr<FileWriterInterface> StdioFileWriter::Open(
     return nullptr;
   }
 
+#ifndef DRACO_OLD_GCC
   return file;
+#else
+  return std::move(file);
+#endif
 }
 
 bool StdioFileWriter::Write(const char *buffer, size_t size) {