examination: skip memdisk on non-BIOS hosts, run per-firmware on x86

examination: skip memdisk on non-BIOS hosts, run per-firmware on x86

This is a combination of two changes:

ts-memdisk-try-append: skip memdisk test on non-BIOS hosts

make-flight: examine: Insist on -bios and -uefi tests on x86

  This will let us skip ts-memdisk-try-append on non-bios platforms
  without risking regression.  It will also definitely spot
  regressions which will occur on any uefi host.

  standalone-generate-dump-flight-runvars reveals the changes are as
  follows:

  New jobs
     test-amd64-i386-examine-bios     test-amd64-i386-examine-uefi
     test-amd64-amd64-examine-bios    test-amd64-amd64-examine-uefi
  added everywhere that has the corresponding plain job, namely
     osstest
     linux-*
     xen-unstable

  These jobs are just like the plain jobs, except that one of
     ,PropEq:Firmware:bios:bios
     ,PropEq:Firmware:bios:uefi
  has been added to the end of all_hostflags.

Signed-off-by: Ian Jackson <iwj@xenproject.org>
Release-Acked-by: Ian Jackson <iwj@xenproject.org>