Add the archive or object file specified by namespec to the list of files to link.
This option may be used any number of times. If namespec is of the form :filename, ld
will search the library path for a file called filename, otherwise it will search the
library path for a file called libnamespec.a.
On systems which support shared libraries, ld may also search for files other than
libnamespec.a. Specifically, on ELF and SunOS systems, ld will search a directory for
a library called libnamespec.so before searching for one called libnamespec.a. (By
convention, a ".so" extension indicates a shared library.) Note that this behavior
does not apply to :filename, which always specifies a file called filename.
So, the files your looking for are
I can't find these files in the Ubuntu package archive, so I guess they were intended to be set up via earlier steps.
Check your work (did you type the command correctly, did the command work?) on the previous steps.