Ubuntu16.04 IL2CPP

I'm trying to use IL2CPP on Ubuntu 16, having installed Unity 2019.3.0f1 and using the default empty project, I'm getting the following error:

In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/5.4.0/../../../../include/c++/5.4.0/atomic:38:
/usr/bin/../lib/gcc/x86_64-linux-gnu/5.4.0/../../../../include/c++/5.4.0/bits/c++0x_warning.h:32:2: error: This file requires compiler and library support for the ISO C++ 2011 standard. This support must be enabled with the -std=c++11 or -std=gnu++11 compiler options.
#error This file requires compiler and library support \

From this post (https://answers.unity.com/questions/1610105/how-to-add-compiler-or-linker-flags-for-il2cpp-inv.html) I added the environment variable and it moved on, but now gives the error:

error: invalid argument '-std=gnu++11' not allowed with 'C/ObjC'

This "just worked" on Ubuntu 18, but unfortunately I need to stick with 16. Is there a cheat sheet on how to get this to work someplace?

 

Upgrading to clang 6.0 resolved the issue.

https://blog.kowalczyk.info/article...est-clang-6.0-on-ubuntu-16.04-xenial-wsl.html