Should be fixed now.
Added the <string.h> to the getopt.c
Don't no why this has its own getopt version.
Probably historicly...

This is the current git on macOS, using clang 14.0.0.
After ./configure, make fails with

gcc -DHAVE_CONFIG_H -I. -I.. -I./../intl -I../intl  -I/usr/local/include  -g -O2 -c -o getopt.o getopt.c
getopt.c:527:30: error: implicitly declaring library function 'strcmp' with type 'int (const char , const char )' [-Werror,-Wimplicit-function-declaration]
      if (optind != argc && !strcmp (argv[optind], "--"))


and

getopt.c:603:7: error: implicitly declaring library function 'strncmp' with type 'int (const char , const char , unsigned long)' [-Werror,-Wimplicit-function-declaration]
        if (!strncmp (p->name, nextchar, nameend - nextchar))


and

getopt.c:606:21: error: implicitly declaring library function 'strlen' with type 'unsigned long (const char *)' [-Werror,-Wimplicit-function-declaration]
                == (unsigned int) strlen (p->name))


Adding #include <string.h> to compat/getopt.c fixes that.
(But why does enscript have its own buggy getopt in the first place?)