Use fdatasync instead of fsync on supported platforms

src/util.cpp

@@ -1111,9 +1111,13 @@ void FileCommit(FILE *fileout)
     fflush(fileout);                // harmless if redundantly called
 #ifdef WIN32
     _commit(_fileno(fileout));
+#else
+    #if defined(__linux__) || defined(__NetBSD__)
+    fdatasync(fileno(fileout));
     #else
     fsync(fileno(fileout));
     #endif
+#endif
 }
 
 int GetFilesize(FILE* file)