Patches for moving from Unikraft v0.20.0 to v0.21.0

[garethodickin]

When rebuilding a design in Unikraft v0.21.0, we compiled a list of patches needed to complete build without error. The affected files are:

      drivers/xen/xencons/console.c
      lib/posix-process/arch/arm64/signal.S
      lib/posix-process/shutdown.c
      lib/ukpod/anon.c
      plat/xen/Makefile.uk
      plat/xen/arm/mm.c
      plat/xen/include/uk/plat/xen/tlb.h

[michpappas]

Most likely due to the refactoring in 0.21.0, and differences in the configuration used in our testing. Generally speaking bugfixes are always welcome, no need for prior discussion :) If, however, these help tracking from your side, also okay.

[michpappas]

As the logs mention signals, please see the reply in #1840 on the general state of signals in arm64. If this is a regression we can probably help if you share your .config.