cross-platform: Fix memmove warning

[obastemur]

This fails on CI now and produces an error. See http://dotnet-ci.cloudapp.net/job/Microsoft_ChakraCore/job/master/job/ubuntu_linux_release_prtest/717/

[obastemur]

@dilijev @mmitche do we have a problem with Ubuntu machine?

First #1550 generated a no issue (under the normal circumstances) : http://dotnet-ci.cloudapp.net/job/Microsoft_ChakraCore/job/master/job/ubuntu_linux_release_prtest/717/

After calling the test again, it was fine..

and then this one : http://dotnet-ci.cloudapp.net/job/Microsoft_ChakraCore/job/master/job/ubuntu_linux_release_prtest/719/

04:18:11 �[1m/mnt/j/workspace/Microsoft_ChakraCore/master/ubuntu_linux_release_prtest/pal/inc/safemath.h:47:10: �[0m�[0;1;31mfatal error: �[0m�[1m'type_traits' file not found�[0m
04:18:11 #include <type_traits>
04:18:11 �[0;1;32m         ^
04:18:11 �[0m[ 20%] Building CXX object lib/Common/Memory/CMakeFiles/Chakra.Common.Memory.dir/ForcedMemoryConstraints.cpp.o

[mmitche]

These machines have been spun up fresh (the machine it last failed on is no longer around) and nothing has changed on that front, so let's try again and see.

It seems unlikely that anything is actually wrong with the machine image itself.

@dotnet-bot test Ubuntu ubuntu_linux_release