Make -ldl -lrt -lpthread implicit for host builds

Instead of requiring every host module to specify -ldl -lrt -lpthread
and then break the mac build because -lrt doesn't exist, make them
implicit to match the behavior of modules built for the device.

Test: m -j checkbuild
Change-Id: I7b5b5289a41cd8f6e7dc2da59400955d867ee783