Please note that this is not stable software at all. Do not expect all rust crates to work without issues on Windows 95! Only minimal testing has been done - please feel free to file issues or PRs if you're crazy enough to test this :)
Most of the fallback/workaround implementations were able to be implemented in a "proper" way (i.e. not checking for Windows version, but actual API availability). So far only 9x/ME needed some specific "is this not NT?"-checks to prevent unneeded extra calls that are known to fail anyways.
Please note that the compiler is compiled for regular x86_64-pc-windows-msvc, so it still has roughly the same requirements as a regular rust install. It is a cross-compiler for rust9x only.
In general, any platform libraries/SDKs that has .lib files that are compatible with the modern MSVC toolsets' linkers should be fine. Static linking should always work, dynamic linking might need additional steps.
Note that panic unwinding needs at least the VC8 (Visual C++ 2005) libraries. If you know why or find a fix, please submit a PR!