configure: Fix googletest depedence
configure: Fix googletest depedence

b4b3247afc020843ebea278bf3c4e1cbebc54968 accidentally added a hard
dependency on googletest. The behavior of PKG_CHECK_MODULES is to fail
if the package is not found if no [action-if-not-found] is provided.
This change provides a no-op [action-if-not-found] so that autodetection
does not fail if not required.

Tested:
    Ran through the unit test suite. Ran through the openbmc build
    process without the googletest dependency to make sure it builds
    now.

Change-Id: I81492833cc88b269a6d9ac1cb55b95da1975d40b
Signed-off-by: William A. Kennington III <30fff5198f4d10ca1117e5f3ec82f3b4b8900d81@google.com>

openbmc/sdbusplus,openbmc/sdbusplus,openbmc/sdbusplus,openbmc/sdbusplus