Merge remote-tracking branch 'remotes/stsquad/tags/pull-testing-and-gdbstub-060520...

Merge remote-tracking branch 'remotes/stsquad/tags/pull-testing-and-gdbstub-060520-1' into staging

Testing and gdbstub updates:

  - travis: drop macosx, tweak ppc64 native
  - cirrus: fix FreeBSD, guard against future breakage
  - gdbstub: support socket debug for linux-user
  - gdbstub: add multiarch tests
  - gdbstub: fixes for m68k

# gpg: Signature made Wed 06 May 2020 09:33:17 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-gdbstub-060520-1:
  target/m68k: fix gdb for m68xxx
  tests/tcg: add a multiarch linux-user gdb test
  tests/guest-debug: use the unix socket for linux-user tests
  gdbstub/linux-user: support debugging over a unix socket
  gdbstub: eliminate gdbserver_fd global
  tests/tcg: drop inferior.was_attached() test
  tests/tcg: better trap gdb failures
  gdbstub: Introduce gdb_get_float64() to get 64-bit float registers
  configure: favour gdb-multiarch if we have it
  .travis.yml: reduce the load on [ppc64] GCC check-tcg
  .cirrus.yml: bootstrap pkg unconditionally
  .cirrus.yml: bump FreeBSD to the current stable release
  .travis.yml: drop MacOSX
  .travis.yml: show free disk space at end of run

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