Collect coverage information for use with gcov.
Coverage is disabled on FreeBSD because the current version of clang
provided by FreeBSD can't successfully link with -ftest-coverage enabled
(the compiler-rt support libs are too old).
Change-Id: Icc444936caa852bfb9a02b37223209319a27a770
Signed-off-by: Daniel Verkamp <daniel.verkamp@intel.com>
