While I am investigating the issue, I suggest using an older compiler.
So far I have not experienced the error you are sharing with Visual Studio Community 2019.
You may install it and configure your batch files to point to that version instead (e.g. compiler-cpp.bat and other batch files should be set to point to C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Auxiliary\Build\vcvarsx86_amd64.bat to generate 64-bit FMUs).
I have also managed to compile E+FMU with
Visual Studio Express 2015 for Windows Desktop (
https://visualstudio.microsoft.com/vs/older-downloads/) by setting the batch files to point to
C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\bin\x86_amd64\vcvarsx86_amd64.bat to generate 64-bit FMUs.
You may try any of those two options and let me know if that works. This may be a temporary solution that should not have any adverse impact on your system setting while debugging is ongoing.