https://bugs.winehq.org/show_bug.cgi?id=43516
--- Comment #3 from Benjamin Hodgetts ben@xnode.org --- Yeah, I did some pretty extensive searching around and could only find maybe 2 references over the last 10 years or so mentioning CFLAGs affecting copy protection, but nothing that ever mentioned the march flag at all which made me suspicious.
The official build guide doesn't seem to mention any specific issues with flags either - https://wiki.winehq.org/Building_Wine#Compiler_Optimizations_.26_Call-Stacks
As AJ said, this could even be a GCC 7 bug rather than a Wine bug.