Make shim_cert.h able to be included more safely.
Make shim_cert.h able to be included more safely.

If you build with ENABLE_SHIM_CERT=1, the include chain right now winds
up meaning shim_cert is defined in a header that gets included in
netboot.c as well, which never uses it:

  In file included from shim.h:125:0,
                   from netboot.c:36:
  shim_cert.h:1:14: error: ‘shim_cert’ defined but not used [-Werror=unused-variable]
   static UINT8 shim_cert[] = {
                ^~~~~~~~~
  cc1: all warnings being treated as errors

So make that okay by adding __attribute__((__unused__)) to the variable
decl.

Signed-off-by: Peter Jones <2e0a021e603479ff81838c00c3b770daca4e0214@redhat.com>

rhinstaller/shim,rhinstaller/shim,rhinstaller/shim