Breaking changes:
To build Lean from source on Windows, it is now necessary to install the
[Windows
SDK](https://developer.microsoft.com/en-us/windows/downloads/windows-sdk/).
The build instructions have been updated to reflect this. Note that the
Windows SDK is **not** needed to compile Lean programs using a Lean
toolchain obtained using `elan`. The Windows SDK is only needed to build
Lean itself from source.
Furthermore, we are dropping support for Windows versions older than
Windows 10 1903 (released in May 2019).
No Windows version that is still supported by Microsoft as part of
mainstream support is affected by this.
The following Windows versions are still supported by Microsoft as part
of commercial extended support but are no longer supported by Lean:
- Windows 10 Enterprise LTSC 2015
- Windows 10 Enterprise LTSC 2016
- Windows 10 Enterprise LTSC 2019
- Windows Server 2019
This PR fixes the documentation error in "Extended Setup Notes", where
the path of builded binary is pointed to
`./build/bin/foo`, but the truly path is `./lake/build/bin/foo`.
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Closes#3094 (`RFC` or `bug` issue number fixed by this PR, if any)
