Backport fixes for aarch64-pc-windows-msvc#46

Merged

alexcrichton merged 2 commits intorust-lang:rustc/10.0-2020-02-05from danielframpton:rustc/aarch64-windows-backport-llvm10

May 5, 2020

+212-67

Commits on Apr 1, 2020

[AArch64] Fix mismatch in prologue and epilogue for funclets on Windows
danielframpton
committed
[AArch64] Change AArch64 Windows EH UnwindHelp object to be a fixed object
danielframpton
committed