std: Fix the return value of Duration::span

The subtraction was erroneously backwards, returning negative durations!

Closes #18925
etc: Don't bundle libctl3d32 on windows

Apparently it's not found on win64!

Closes #18928
auto merge of #18926 : alexcrichton/rust/issue-18925, r=huonw

The subtraction was erroneously backwards, returning negative durations!

Closes #18925
auto merge of #18929 : alexcrichton/rust/issue-18928, r=brson

Apparently it's not found on win64!

Closes #18928