Downstream-only patch.
Upstream bind9 development has changed configure significantly:
https://gitlab.isc.org/isc-projects/bind9

From 035224d94d4cf93257cf5440a2e4e129540e81e8 Mon Sep 17 00:00:00 2001
From: Arjun Shankar <arjun@redhat.com>
Date: Thu, 20 Apr 2023 15:34:01 +0200
Subject: [PATCH] Port to C99

---
 bind/bind-9.11.36/configure    | 14 +++++++-------
 bind/bind-9.11.36/configure.ac | 14 +++++++-------
 2 files changed, 14 insertions(+), 14 deletions(-)

diff --git a/bind/bind-9.11.36/configure b/bind/bind-9.11.36/configure
index 368112f..c50d873 100755
--- a/bind/bind-9.11.36/configure
+++ b/bind/bind-9.11.36/configure
@@ -20016,7 +20016,7 @@ else
 #include <sys/socket.h>
 #include <netinet/in.h>
 #include <arpa/inet.h>
-main() {
+int main() {
 char a[16],b[64]; return(inet_ntop(AF_INET6, a, b, sizeof(b)) == (char*)0);}
 _ACEOF
 if ac_fn_c_try_run "$LINENO"; then :
@@ -20056,7 +20056,7 @@ else
 #include <sys/socket.h>
 #include <netinet/in.h>
 #include <arpa/inet.h>
-main() { char a[16]; return (inet_pton(AF_INET, "1.2.3", a) == 1 ? 1 :
+int main() { char a[16]; return (inet_pton(AF_INET, "1.2.3", a) == 1 ? 1 :
 			     inet_pton(AF_INET, "1.2.3.04", a) == 1 ? 1 :
 			     (inet_pton(AF_INET6, "::1.2.3.4", a) != 1)); }
 _ACEOF
@@ -21346,7 +21346,7 @@ else
 #include <sys/types.h>
 #include <sys/time.h>
 #include <sys/resource.h>
-main() { struct rlimit r; exit(!(sizeof(r.rlim_cur) == sizeof(int)));}
+int main() { struct rlimit r; exit(!(sizeof(r.rlim_cur) == sizeof(int)));}
 _ACEOF
 if ac_fn_c_try_run "$LINENO"; then :
   { $as_echo "$as_me:${as_lineno-$LINENO}: result: int" >&5
@@ -21363,7 +21363,7 @@ else
 #include <sys/types.h>
 #include <sys/time.h>
 #include <sys/resource.h>
-main() { struct rlimit r; exit(!(sizeof(r.rlim_cur) == sizeof(long int)));}
+int main() { struct rlimit r; exit(!(sizeof(r.rlim_cur) == sizeof(long int)));}
 _ACEOF
 if ac_fn_c_try_run "$LINENO"; then :
   { $as_echo "$as_me:${as_lineno-$LINENO}: result: long int" >&5
@@ -21380,7 +21380,7 @@ else
 #include <sys/types.h>
 #include <sys/time.h>
 #include <sys/resource.h>
-main() { struct rlimit r; exit((!sizeof(r.rlim_cur) == sizeof(long long int)));}
+int main() { struct rlimit r; exit((!sizeof(r.rlim_cur) == sizeof(long long int)));}
 _ACEOF
 if ac_fn_c_try_run "$LINENO"; then :
   { $as_echo "$as_me:${as_lineno-$LINENO}: result: long long int" >&5
@@ -21759,7 +21759,7 @@ int
 main ()
 {
 
-				main() { asm("ics"); exit(0); }
+				int main() { asm("ics"); exit(0); }
 
   ;
   return 0;
@@ -21782,7 +21782,7 @@ else
   cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 
-				main() { asm("ics"); exit(0); }
+				int main() { asm("ics"); exit(0); }
 
 _ACEOF
 if ac_fn_c_try_run "$LINENO"; then :
diff --git a/bind/bind-9.11.36/configure.ac b/bind/bind-9.11.36/configure.ac
index 030c4d7..e74af09 100644
--- a/bind/bind-9.11.36/configure.ac
+++ b/bind/bind-9.11.36/configure.ac
@@ -3274,7 +3274,7 @@ AC_TRY_RUN([
 #include <sys/socket.h>
 #include <netinet/in.h>
 #include <arpa/inet.h>
-main() {
+int main() {
 char a[16],b[64]; return(inet_ntop(AF_INET6, a, b, sizeof(b)) == (char*)0);}],
 	[AC_MSG_RESULT(yes)
 	ISC_PLATFORM_NEEDNTOP="#undef ISC_PLATFORM_NEEDNTOP"],
@@ -3297,7 +3297,7 @@ AC_TRY_RUN([
 #include <sys/socket.h>
 #include <netinet/in.h>
 #include <arpa/inet.h>
-main() { char a[16]; return (inet_pton(AF_INET, "1.2.3", a) == 1 ? 1 :
+int main() { char a[16]; return (inet_pton(AF_INET, "1.2.3", a) == 1 ? 1 :
 			     inet_pton(AF_INET, "1.2.3.04", a) == 1 ? 1 :
 			     (inet_pton(AF_INET6, "::1.2.3.4", a) != 1)); }],
 	[AC_MSG_RESULT(yes)
@@ -3901,7 +3901,7 @@ AC_TRY_RUN([
 #include <sys/types.h>
 #include <sys/time.h>
 #include <sys/resource.h>
-main() { struct rlimit r; exit(!(sizeof(r.rlim_cur) == sizeof(int)));}],
+int main() { struct rlimit r; exit(!(sizeof(r.rlim_cur) == sizeof(int)));}],
 [AC_MSG_RESULT(int)
 ISC_PLATFORM_RLIMITTYPE="#define ISC_PLATFORM_RLIMITTYPE int"],
 [
@@ -3909,7 +3909,7 @@ AC_TRY_RUN([
 #include <sys/types.h>
 #include <sys/time.h>
 #include <sys/resource.h>
-main() { struct rlimit r; exit(!(sizeof(r.rlim_cur) == sizeof(long int)));}],
+int main() { struct rlimit r; exit(!(sizeof(r.rlim_cur) == sizeof(long int)));}],
 [AC_MSG_RESULT(long int)
 ISC_PLATFORM_RLIMITTYPE="#define ISC_PLATFORM_RLIMITTYPE long int"],
 [
@@ -3917,7 +3917,7 @@ AC_TRY_RUN([
 #include <sys/types.h>
 #include <sys/time.h>
 #include <sys/resource.h>
-main() { struct rlimit r; exit((!sizeof(r.rlim_cur) == sizeof(long long int)));}],
+int main() { struct rlimit r; exit((!sizeof(r.rlim_cur) == sizeof(long long int)));}],
 [AC_MSG_RESULT(long long int)
 ISC_PLATFORM_RLIMITTYPE="#define ISC_PLATFORM_RLIMITTYPE long long int"],
 [AC_MSG_ERROR([unable to determine sizeof rlim_cur])
@@ -4117,7 +4117,7 @@ case "$enable_atomic" in
 			if test "X$GCC" = "Xyes"; then
 				AC_MSG_CHECKING([if asm("ics"); works])
 				AC_TRY_COMPILE(,[
-				main() { asm("ics"); exit(0); }
+				int main() { asm("ics"); exit(0); }
 				],
 				[AC_MSG_RESULT(yes)
 				 use_atomic=yes],
@@ -4125,7 +4125,7 @@ case "$enable_atomic" in
 				saved_cflags="$CFLAGS"
 				CFLAGS="$CFLAGS -Wa,-many"
 				AC_TRY_RUN([
-				main() { asm("ics"); exit(0); }
+				int main() { asm("ics"); exit(0); }
 				],
 				[AC_MSG_RESULT([yes, required -Wa,-many])
 				 use_atomic=yes],
-- 
2.40.0