rebuild autopkgtest never succeeds

[Steve Langasek]

The linux-oracle package never succeeds its rebuild autopkgtest.

  HOSTCC scripts/selinux/genheaders/genheaders
In file included from /tmp/autopkgtest.vlURUK/build.51y/src/scripts/selinux/genh
eaders/genheaders.c:19:
/tmp/autopkgtest.vlURUK/build.51y/src/security/selinux/include/classmap.h:247:2:
 error: #error New address family defined, please update secclass_map.
 #error New address family defined, please update secclass_map.
  ^~~~~
make[6]: *** [scripts/Makefile.host:90: scripts/selinux/genheaders/genheaders] E
rror 1
make[2]: Leaving directory '/tmp/autopkgtest.vlURUK/build.51y/src/debian/build/build-oracle'
make[1]: Leaving directory '/tmp/autopkgtest.vlURUK/build.51y/src'
make[5]: *** [/tmp/autopkgtest.vlURUK/build.51y/src/scripts/Makefile.build:604: scripts/selinux/genheaders] Error 2
make[4]: *** [/tmp/autopkgtest.vlURUK/build.51y/src/scripts/Makefile.build:604: scripts/selinux] Error 2
make[3]: *** [/tmp/autopkgtest.vlURUK/build.51y/src/Makefile:589: scripts] Error 2
make[2]: *** [/tmp/autopkgtest.vlURUK/build.51y/src/Makefile:278: __build_one_by_one] Error 2

(http://autopkgtest.ubuntu.com/packages/l/linux-oracle/eoan/amd64)

Since this test is skipped when linux-meta-oracle is the trigger, these failures show up as regressions and clog proposed-migration.

Either the test should be fixed so that the package can actually be rebuilt via the autopkgtest, or the autopkgtest should always be skipped for this custom kernel.