PEL: Simplify test makefile
PEL: Simplify test makefile

The test helpers pel_utils.cpp and paths.cpp were getting compiled for
each testcase that uses them.  Instead, use LDADD so they only get
compiled once.

Signed-off-by: Matt Spinler <c000c989d08c98662d98f15448f11de169feb92d@us.ibm.com>
Change-Id: I86e6590ef67630de0515f6df83dbe5ff7ef12768

openbmc/phosphor-logging,openbmc/phosphor-logging,openbmc/phosphor-logging,openbmc/phosphor-logging