makefile:4: *** missing separator. Stop

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.

Example:

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  $@  $<$ 
## 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

On VS Code, just click the "Space: 4" on the downright corner and change it to tab when editing your Makefile.

You should always write command after a Tab and not white space.

This applies to gcc line (line #4) in your case. You need to insert tab before gcc.

Also replace \rm -fr ll with rm -fr ll. Insert tabs before this command too.