makefile-use-curly-braces-for-macros-p

makefile-use-curly-braces-for-macros-p is a variable defined in `make-mode.el'.
Its value is

nil

Documentation:
Controls the style of generated macro references.
Non-nil means macro references should use curly braces, like `${this}'.
nil means use parentheses, like `$(this)'.

You can customize this variable.