Building V5 runtime and win32 api as native build on Windows

There are no build instructions for these How can I
build them from source as a native Windows build?

I'm doing experiments with building a MinGW gcc 7.1
that uses sjlj exceptions. I know very little about how
exceptions are done by gcc, but I expect that inconsistent
exception handling methods will cause trouble, so I'm
trying to rebuild everything I might possibly use with
my sjlj test version of gcc 7.1
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