$ cat Makefile
debug:
        @set | grep MAKEFLAGS
        @make subtask

subtask:
        @set | grep MAKEFLAGS
$ make debug
BASH_EXECUTION_STRING='set | grep MAKEFLAGS'
MAKEFLAGS=
make[1]: Entering directory '/Users/oklischat'
BASH_EXECUTION_STRING='set | grep MAKEFLAGS'
MAKEFLAGS=w
make[1]: Leaving directory '/Users/oklischat'
$ make FOO=hello debug
BASH_EXECUTION_STRING='set | grep MAKEFLAGS'
MAKEFLAGS=' -- FOO=hello'
make[1]: Entering directory '/Users/oklischat'
BASH_EXECUTION_STRING='set | grep MAKEFLAGS'
MAKEFLAGS='w -- FOO=hello'
make[1]: Leaving directory '/Users/oklischat'
$