llvm-link takes several LLVM bitcode files and links them together into a
single LLVM bitcode file. It writes the output file to standard output, unless
the -o option is used to specify a filename.
llvm-link attempts to load the input files from the current directory. If
that fails, it looks for each file in each of the directories specified by the
-L options on the command line. The library search paths are global; each
one is searched for every input file if necessary. The directories are searched
in the order they were specified on the command line.
If llvm-link succeeds, it will exit with 0. Otherwise, if an error
occurs, it will exit with a non-zero value.