The following was disallowed:
add_library(iface INTERFACE)
target_link_libraries(iface PUBLIC)
just due to the mention of the `PUBLIC` keyword. Instead, only error if
there are actually `PUBLIC` dependencies specified (and analogously for
other restrictions).
Update tests to expect this new behavior.
Not all of these commands accept non-compilable (i.e., IMPORTED)
targets, so those calls are currently just commented out. If they ever
do start to accept them, the tests should be enabled.