patch 8.0.0280: problem setting multi-byte environment var on MS-Windows
Problem: On MS-Windows setting an environment variable with multi-byte
strings does not work well.
Solution: Use wputenv when possible. (Taro Muraoka, Ken Takata)
7c23d1d9d9cc
This allows executables to be found by :!, system(), and executable() if
they live next to ("sibling" to) nvim.exe. This is what gvim on Windows
does, and also matches the behavior of Win32 SearchPath().
c4a249a736/src/os_win32.c (L354-L370)