Install only lldb-server in the target image

[davidepianca98]

Is your feature request related to a problem? Please describe.
We would like to be able to install only the debugger lldb-server in the target image to save space, since we don't need the full compiler on the target. Right now add lldb-server to IMAGE_INSTALL installs all the clang, llvm binaries and libraries. We are using the kirkstone branch.

Describe the solution you'd like
It would be very nice if specifying lldb-server would install only the debugger like gdbserver does right now.

Describe alternatives you've considered
Otherwise we would be fine with a way to remove unneeded files in a bbappend if you can suggest how we can do that.