tell them how to break assignments long lines

[jidanni]

Your Make Info document does not tell the user how to break his
variable assignments without tears. So mention it explicitly right
upon the relevant page.

$ make
this is long line 1 that I would li ke to break
this is long line 2 that I would like to break
$ cat makefile
A=this is long line 1 that I would li\
ke to break
B=this is long line 2 that I would li$(\
)ke to break

g:
        @echo $A
        @echo $B