perl-Net-IDN-Encode-2.500-18.fc40 fails to build in Fedora 40 because of missing function prototypes:

gcc -I/usr/lib64/perl5/CORE '-DVERSION="2.500"' '-DXS_VERSION="2.500"' -fPIC -c -D_REENTRANT -D_GNU_SOURCE -O2 '-flto=auto' -ffat-lto-objects -fexceptions -g -grecord-gcc-switches -pipe -Wall -Wno-complain-wrong-lang '-Werror=format-security' '-Werror=implicit-function-declaration' '-Werror=implicit-int' '-Wp,-U_FORTIFY_SOURCE,-D_FORTIFY_SOURCE=3' -Wp,-D_GLIBCXX_ASSERTIONS '-specs=/usr/lib/rpm/redhat/redhat-hardened-cc1' -fstack-protector-strong '-specs=/usr/lib/rpm/redhat/redhat-annobin-cc1' -m64 '-mtune=generic' -fasynchronous-unwind-tables -fstack-clash-protection -fcf-protection -fno-omit-frame-pointer -mno-omit-leaf-frame-pointer -fwrapv -fno-strict-aliasing -I/usr/local/include -D_LARGEFILE_SOURCE '-D_FILE_OFFSET_BITS=64' -O2 '-flto=auto' -ffat-lto-objects -fexceptions -g -grecord-gcc-switches -pipe -Wall '-Werror=format-security' '-Werror=implicit-function-declaration' '-Werror=implicit-int' '-Wp,-U_FORTIFY_SOURCE,-D_FORTIFY_SOURCE=3' -Wp,-D_GLIBCXX_ASSERTIONS '-specs=/usr/lib/rpm/redhat/redhat-hardened-cc1' -fstack-protector-strong '-specs=/usr/lib/rpm/redhat/redhat-annobin-cc1' -m64 '-mtune=generic' -fasynchronous-unwind-tables -fstack-clash-protection -fcf-protection -fno-omit-frame-pointer -mno-omit-leaf-frame-pointer -g -o lib/Net/IDN/Punycode.o lib/Net/IDN/Punycode.c
lib/Net/IDN/Punycode.xs: In function ‘XS_Net__IDN__Punycode_decode_punycode’:
lib/Net/IDN/Punycode.xs:232:36: warning: array subscript has type ‘char’ [-Wchar-subscripts]
  232 |                     dc = dec_digit[*in_p++];                    /* we already know it's in 0..127 */
      |                                    ^~~~~~~
lib/Net/IDN/Punycode.xs:256:19: error: implicit declaration of function ‘uvuni_to_utf8_flags’; did you mean ‘uvchr_to_utf8_flags’? [-Werror=implicit-function-declaration]
  256 |                   uvuni_to_utf8_flags((U8*)skip_p, n, UNICODE_ALLOW_ANY);
      |                   ^~~~~~~~~~~~~~~~~~~

This is triggered by upgrading redhat-rpm-config from 266-1.fc40 to 267-1.fc40 which added -Werror=implicit-function-declaration compiler option as a preparation for stricter GCC 14.