freadahead.c: In function 'freadahead':

freadahead.c:92:3: error: #error "Please port gnulib freadahead.c to your platform! Look at the definition of fflush, fread, ungetc on your system, then report this to bug-gnulib."

   92 |  #error "Please port gnulib freadahead.c to your platform! Look at the definition of fflush, fread, ungetc on your system, then report this to bug-gnulib."

      |   ^~~~~

make[3]: *** [Makefile:1910: freadahead.o] Error 1

make[3]: Leaving directory '/opt/build/m4-1.4.18/lib'

make[2]: *** [Makefile:1674: all] Error 2

make[2]: Leaving directory '/opt/build/m4-1.4.18/lib'

make[1]: *** [Makefile:1572: all-recursive] Error 1

make[1]: Leaving directory '/opt/build/m4-1.4.18'

make: *** [Makefile:1528: all] Error 2