How to prompt user for [y/n] in my makefile (with pure make syntaxis)?

I am writing a makefile that should work on both Windows and Linux. So wherever possible, I avoid OS-specific shell commands.

Here is a snippet from my makefile with the clean function at the end:

# OS specific part
# -----------------
ifeq ($(OS),Windows_NT)
    RM = del /F /Q
    RMDIR = -RMDIR /S /Q
    MKDIR = -mkdir
    ERRIGNORE = 2>NUL || (exit 0)
    SEP=\\
else
    RM = rm -rf 
    RMDIR = rm -rf 
    MKDIR = mkdir -p
    ERRIGNORE = 2>/dev/null
    SEP=/
endif
PSEP = $(strip $(SEP))

# Definitions for nullstring and space
# -------------------------------------
nullstring :=
space := $(nullstring) #End

# Lists of all files and folders to keep or remove
# -------------------------------------------------
buildFiles_toKeep := ...    # I wrote some scripts to
buildDirs_toKeep := ...     # automatically generate
buildFiles_toRemove := ...  # these lists. But that would lead
buildDirs_toRemove := ...   # us too far here.


.PHONY: clean
clean:
    @echo.
    @echo ----------------------------------------------------------
    @echo.$(space)        __         **************    $(space)
    @echo.$(space)      __\ \___     * make clean *    $(space)
    @echo.$(space)      \ _ _ _ \    **************    $(space)
    @echo.$(space)       \_`_`_`_\                     $(space)
    @echo.$(space)                                     $(space)
    @echo.$(space)Keep these files:
    @echo.$(space)  $(buildFiles_toKeep)
    @echo.$(space)
    @echo $(space)Keep these directories:
    @echo.$(space)  $(buildDirs_toKeep)
    @echo.$(space)
    @echo.$(space)Remove these files:
    @echo.$(space)  $(buildFiles_toRemove)
    $(RM) $(buildFiles_toRemove)
    @echo.
    @echo.$(space)Remove these directories:
    @echo.$(space)  $(buildDirs_toRemove)
    $(RMDIR) $(buildDirs_toRemove)
    @echo.
@echo ----------------------------------------------------------

This makefile works great. Both on Windows and Linux, it replaces $(RM) and $(RMDIR) with the proper shell commands to delete files and folders. But I would like to prompt the user such that he/she can press Y or N. I would not want to delete files he/she wants to keep. I've tried to insert some batch-commands into the recipees of the clean target that prompt the user for input. But the prompt is not shown. Perhaps because GNU make defers the input stream.

I wonder if it is possible to generate a [Y/N] prompt with 'pure' make syntaxis (no OS-specific shell commands). I know that the make language has its limitations. Perhaps a clever solution can work on one operating system (eg. Linux) and be ported with minimal overhead to another (eg. Windows).

Anyone an idea?

EDIT :

I got referred to this link: How do I get `make` to prompt the user for a password and store it in a Makefile variable?

Gnu make will create the variable PASSWORD by prompting the user:

$ cat Makefile 
PASSWORD ?= $(shell bash -c 'read -s -p "Password: " pwd; echo $$pwd')

This way of prompting the user for input works fine as long as you want the prompt to appear at the moment your makefile is parsed. But my case is different. I want to prompt the user when the makefile is already running, in other words, when the recipees in the makefile are executing.

EDIT :

Prompting the user won't be possible when you run make multi-threaded. So I'm perfectly fine with calling the clean function single-threaded:

    >> make clean -j1

After all, the clean function doesn't take long to finish. I do not intend to prompt the user for anything in the build function, so that can be executed multi-threaded :-)

    >> make all -j8 --output-sync=target