make file escape

$ cat Makefile
slash.txt:
    echo "\\slash{\\another{po}}"
    echo "$SHELL"

$ echo "\\slash{\\another{po}}"
\slash{\another{po}}

$ echo "$SHELL"
/bin/bash

$ make slash.txt
echo "\\slash{\\another{po}}"
\slash{nother{po}}
echo "HELL"
HELL