Since 9c430f6b changed some files to no longer include config.h, building with glibc and an -std= in CFLAGS fails because getopt, used in support/bashversion.c and mksyntax.c, is guarded by _POSIX_C_SOURCE >= 2 || _XOPEN_SOURCE
support/bashversion.c:69:17: warning: implicit declaration of function 'getopt' [-Wimplicit-function-declaration] 69 | while ((opt = getopt(argc, argv, "hrvmpslx")) != EOF) | ^~~~~~ support/bashversion.c:103:11: error: 'optind' undeclared (first use in this function) 103 | argc -= optind; | ^~~~~~