Revert "stage1: upgrade to new LLVM sret attribute requirement"

This reverts commit 685b5c26b703d54381a74b71361816ad85ec8584.

@LemonBoy has a better patch, so reverting this to merge that one.
431801707fAndrew Kelley committed on 2/26/2021, 8:47:33 PMparent685b5c2
3 files changedLine totals unavailable