This gains some bugfixes, especially:

- it fixes the introspection of array options.  While technically we
still support Meson 0.58.2, this issue only appears when adding a new
option and not if the user is just building QEMU.  In the relatively
rare case of a contributor using --meson to point to a 0.58 version,
review can catch spurious changes to scripts/meson-buildoptions.sh
easily.

- it fixes "meson test" when it is not the process group leader.  Make is
the process group leader when "make check" invokes "meson test", so this
is a requirement for using it as a test harness.

Tested-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>