build-unit-test-docker: Ensure pthread flag is -pthread
build-unit-test-docker: Ensure pthread flag is -pthread

googletest and googlemock incorrectly use CMAKE_THREAD_LIBS_INIT in the
Cflags declaration for their .pc files. We can make this work by
ensuring that CMAKE_THREAD_LIBS_INIT is always -pthread which works as a
Cflag and Linker flag.

See google/googletest#2006

Change-Id: Ib53d23c34e61e986e14e9e2a41a092b4c8e545af
Signed-off-by: William A. Kennington III <30fff5198f4d10ca1117e5f3ec82f3b4b8900d81@google.com>

openbmc/openbmc-build-scripts,openbmc/openbmc-build-scripts