Fix building with updated ENFORCE_UNIQUE_SYMBOLS behaviour

Fix building with updated ENFORCE_UNIQUE_SYMBOLS behaviour

The patch "build: provide option to disambiguate symbol names" changes
ENFORCE_UNIQUE_SYMBOLS so that gcc generates output to a temporary file
and then objcopy is used to create the final object file. This breaks
livepatch-build's interposition of GCC to capture the changed object
files so intercept calls to objcopy as well to capture the final object
files.

While in the area, add a couple of extra object files to be ignored when
patching.

Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com>