Merge remote-tracking branch...

Merge remote-tracking branch 'remotes/stsquad/tags/pull-testing-and-semihosting-090120-2' into staging

Testing fixes and semiconsole support:

  - build fix (missing x86-iommu stubs)
  - python fixes for freebsd and OSX
  - nicer reporting of acceptance failures
  - fix build nesting of fp-test (breaks bsds)
  - semihosting clean-ups
  - support for blocking semihosting console

# gpg: Signature made Thu 09 Jan 2020 11:42:51 GMT
# 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-semihosting-090120-2:
  tests/tcg: add user version of dumb-as-bricks semiconsole test
  tests/tcg: extract __semi_call into a header and expand
  tests/tcg: add a dumb-as-bricks semihosting console test
  semihosting: add qemu_semihosting_console_inc for SYS_READC
  target/arm: only update pc after semihosting completes
  target/arm: remove unused EXCP_SEMIHOST leg
  testing: don't nest build for fp-test
  travis.yml: install homebrew python for OS X
  travis.yml: duplicate before_script for MacOSX
  travis.yml: Detach build and test steps
  travis.yml: avocado: Print logs of non-pass tests only
  freebsd: use python37
  tests/vm: update openbsd to release 6.6
  hw/i386/x86-iommu: Add missing stubs

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