Merge remote-tracking branch 'remotes/stsquad/tags/pull-testing-230719-4' into staging

Final testing updates:

  - docker sphinx updates
  - windows build re-enabled in CI
  - travis_retry for make check
  - build fixes
  - docker cache fixes

# gpg: Signature made Tue 23 Jul 2019 17:20:16 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-230719-4: (23 commits)
  tests/docker: Refresh APT cache before installing new packages on Debian
  tests/qemu-iotests: Don't use 'seq' in the iotests
  tests/qemu-iotests/group: Remove some more tests from the "auto" group
  tests/qemu-iotests/check: Allow tests without groups
  tests/docker: invoke the DEBUG shell with --noprofile/--norc
  travis: enable travis_retry for check phase
  hw/i386: also turn off VMMOUSE is VMPORT is disabled
  NSIS: Add missing firmware blobs
  tests/docker: Let the test-mingw test generate a NSIS installer
  buildsys: The NSIS Windows build requires qemu-nsis.bmp installed
  buildsys: The NSIS Windows build requires the documentation installed
  tests/docker: Install texinfo in the Fedora image
  tests/docker: Set the correct cross-PKG_CONFIG_PATH in the MXE images
  tests/docker: Install the NSIS tools in the MinGW capable images
  tests/docker: Install Sphinx in the Debian images
  shippable: re-enable the windows cross builds
  tests/dockerfiles: update the win cross builds to stretch
  tests/migration-test: don't spam the logs when we fail
  tests/docker: Install Ubuntu images noninteractively
  tests/docker: Install Sphinx in the Fedora image
  ...

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