configure: Add -Wno-psabi

configure: Add -Wno-psabi

On aarch64, gcc 9.3 is generating

qemu/exec.c: In function ‘address_space_translate_iommu’:
qemu/exec.c:431:28: note: parameter passing for argument of type \
  ‘MemTxAttrs’ {aka ‘struct MemTxAttrs’} changed in GCC 9.1

and many other repetitions.  This structure, and the functions
amongst which it is passed, are not part of a QEMU public API.
Therefore we do not care how the compiler passes the argument,
so long as the compiler is self-consistent.

The only portion of QEMU which does have a public api, and so
must have a stable abi, is "qemu/plugin.h".  We test this by
forcing -Wpsabi in tests/plugin/Makefile.

Buglink: https://bugs.launchpad.net/qemu/+bug/1881552
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20200617201309.1640952-6-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>