The configuration scripts for that directory (lgmon3) use /usr/bin/glib-gettextize (from opt/glib), which expects /usr/share/glib-2.0/gettext/ to exist (which it doesn't). You could add a symlink with that name that points to /usr/share/gettext (a directory installed with opt/glib), but it will fail later in the build process (I forgot why).
The first 2 sed calls disable the gettext support from lgmon3. One from configure and one from makefile. I've guessed you won't need it.
The 3rd sed is useful because there is a symbol used in two source files with the same name (GET_PROTOCOL) without being declared "for internal use only" :) (static), so when those two compiled sources are linked together, the latest versions of GNU linker (from these years of AI & machine learning & going to Mars :) is smart enough to "think" that one module might want to access GET_PROTOCOL from the other module (or the other way around, or who knows how many access combinations are possible, especially now that the quantum computer is already here :), so it doesn't build the final object (for our own good) until we state our "intentions" :D
My guess is that lgmon3 is too old for these new build tools (or the other way around :), and while I was curious why they fail to build, I've stopped at the first or second fix I could came up with.
Have fun! :)