property_contexts: don't delete intermediate on failure

When property_contexts fails to build, the file is deleted
leaving only the error message for debugging. Build
property_contexts and general variant as a temporary
intermediate before running checkfc.

Change-Id: I431d6f4494fa119c1873eab0e77f0eed3fb5754e
Signed-off-by: William Roberts <william.c.roberts@intel.com>