SCons: Use default env["ENV"] and prepend PATH to it

See discussion in #46814. Now going with the safe option again (like in 3.2)
as it turns out that we can't rely on user environments on Windows, since each
shell has a different set of env variables (especially the ones necessary to
use MSVC).

SCons does its own magic when we don't pass it an `ENV` dictionary, so we
should preserve it and only add things in a second step.

Fixes this warning when compiling with MSVC using git-bash.exe:
```
Missing environment variable: WindowsSdkDir
```

Possibly fixes build issues when having both MinGW and MSVC installed and an
older SCons version.

0 files changed, 0 insertions, 0 deletions