Make has a feature where starting a line with a tab and a minus sign will ignore errors on that line: https://www.gnu.org/software/make/manual/html_node/Errors.html
However, if the command whose errors are meant to be ignored starts with an "l", `autoscan` will think it's a library that the user is trying to link with, and thus needs to be checked. Say I have the following Makefile in a directory:

$ cat Makefile
symlinks:
        -ln -s foo bar
$

If I then run `autoscan`, it will produce a `configure.scan` file that looks like this:

$ cat configure.scan
#                                               -*- Autoconf -*-
# Process this file with autoconf to produce a configure script.

AC_PREREQ([2.72])
AC_INIT([FULL-PACKAGE-NAME], [VERSION], [BUG-REPORT-ADDRESS])

# Checks for programs.

# Checks for libraries.
# FIXME: Replace 'main' with a function in '-ln':
AC_CHECK_LIB([n], [main])

# Checks for header files.

# Checks for typedefs, structures, and compiler characteristics.

# Checks for library functions.

AC_CONFIG_FILES([Makefile])
AC_OUTPUT

However, there is no actual "libn" that needs to be linked with, so `autoscan` shouldn't suggest checking for it. I think a decent heuristic to tell these apart would be that if a "-l" sequence in a Makefile is preceded by a tab immediately following the start of a line, it's probably a command rather than a library.