make has a very stupid relationship with tabs. All actions of every rule are identified by tabs. And, no, four spaces don’t make a tab. Only a tab makes a tab.
To check, I use the command
cat -e -t -v makefile_name.
It shows the presence of tabs with
^I and line endings with
$. Both are vital to ensure that dependencies end properly and tabs mark the action for the rules so that they are easily identifiable to the make utility.
Kaizen ~/so_test $ cat -e -t -v mk.t all:ll$ ## here the $ is end of line ... $ ll:ll.c $ ^Igcc -c -Wall -Werror -02 c.c ll.c -o ll [email protected] $<$ ## the ^I above means a tab was there before the action part, so this line is ok . $ clean :$ \rm -fr ll$ ## see here there is no ^I which means , tab is not present .... ## in this case you need to open the file again and edit/ensure a tab ## starts the action part