It's not really something you can "link" to tho? But the basic loop of development in most cases (in compiled languages) is making a code change, then building the software (or tests), and then running the software (or tests) to check that your change did what it was supposed to do.
Building the software is divided into two steps; compiling your source files into object files, then linking those object files together into an executable. As a project grows, the time taken by the compile step in this development loop stays roughly constant; if you only change a single source file, only that source file has to be recompiled. However, the link step has to link together all your object files, from scratch, every time, so the time taken by the link step grows roughly linearly as the project size grows.
Since mainstream linkers are fairly slows, an incremental build of huge projects is generally dominated by the link step. I've personally experienced the pain of making a small change to Chromium, waiting a second or so for the source file I changed to be recompiled, then waiting a minute or two for the linker to go through every single object file and produce the final executable. Mold would have reduced the build time in the development loop from minutes to seconds.
I hope that helped.