[Issue 23193] druntime/win32.mak contains no instructions for how to build druntime

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=23193

--- Comment #1 from Walter Bright <bugzilla at digitalmars.com> ---
For example, how do I set the bootstrap dmd compiler?

What commands do I pass to make?

What make.exe is run?

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