Fix must be taken with a grain of salt, this will fix the
issue on win10 1903+ by specifying an active codepage in
the application manifest.

What broke? OpenVDB uses boosts memory mapped files
which call CreateFileA in the backend when you feed it a
regular string. I think there may be support for wide
strings in boost, but openvdb is not using that.

Now MS didn't implement the whole API twice, what happens
when you call the A variant, is the A variants convert the
input to wide with whatever codepage (CP_APC previously
only changable on a system wide basis) is set, and call
the W function. Win10 1903 added a way to change this
codepage on a per application basis by specifying it
in the manifest.

for stdlib io (fopen+if_stream'n'friends) it's sufficient
to call setlocale(LC_ALL, ".utf8"); but that's a story
for a different diff.

not sure how i feel only being able to fix it on 1903+ but
while BLI_get_short_name works, the number of places that
call openvdb::io::file::open is very much not 1, and some
of those places are beyond our control (ie USD/Mantaflow)