Merge remote-tracking branch 'remotes/stsquad/tags/pull-testing-and-misc-110720-2...

Merge remote-tracking branch 'remotes/stsquad/tags/pull-testing-and-misc-110720-2' into staging

Testing and misc build updates:

  - tests/vm support for aarch64 VMs
  - tests/tcg better cross-compiler detection
  - update docker tooling to support registries
  - update docker support for xtensa
  - gitlab build docker images and store in registry
  - gitlab use docker images for builds
  - a number of skipIf updates to support move
  - linux-user MAP_FIXED_NOREPLACE fix
  - qht-bench compiler tweaks
  - configure fix for secret keyring
  - tsan fiber annotation clean-up
  - doc updates for mttcg/icount/gdbstub
  - fix cirrus to use brew bash for iotests
  - revert virtio-gpu breakage
  - fix LC_ALL to avoid sorting changes in iotests

# gpg: Signature made Sat 11 Jul 2020 15:56:42 BST
# gpg:                using RSA key 6685AE99E75167BCAFC8DF35FBD0DB095A9E2A44
# gpg: Good signature from "Alex Bennée (Master Work Key) <alex.bennee@linaro.org>" [full]
# Primary key fingerprint: 6685 AE99 E751 67BC AFC8  DF35 FBD0 DB09 5A9E 2A44

* remotes/stsquad/tags/pull-testing-and-misc-110720-2: (50 commits)
  iotests: Set LC_ALL=C for sort
  Revert "vga: build virtio-gpu as module"
  tests: fix "make check-qtest" for modular builds
  .cirrus.yml: add bash to the brew packages
  tests/docker: update toolchain set in debian-xtensa-cross
  tests/docker: fall back more gracefully when pull fails
  docs: Add to gdbstub documentation the PhyMemMode
  docs/devel: add some notes on tcg-icount for developers
  docs/devel: convert and update MTTCG design document
  tests/qht-bench: Adjust threshold computation
  tests/qht-bench: Adjust testing rate by -1
  travis.yml: Test also the other targets on s390x
  shippable: pull images from registry instead of building
  testing: add check-build target
  containers.yml: build with docker.py tooling
  gitlab: limit re-builds of the containers
  tests: improve performance of device-introspect-test
  gitlab: add avocado asset caching
  gitlab: enable check-tcg for linux-user tests
  linux-user/elfload: use MAP_FIXED_NOREPLACE in pgb_reserved_va
  ...

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>