[CMake] target_link_libraries external library

[Juan Sanchez]

Hello,

How do you add an externally library for linking into a target?  I am
getting something like this from TARGET_LINK_LIBRARIES?

CMake Error: Attempt to add link library "/bar/linux-x86/opt/foo.a" to
target "waterlooApps" which is not built by this project.

Thanks,

Juan