Run one test with -Werror to catch warnings.

.github/setup_ci.sh

@@ -20,7 +20,7 @@ lsb_release -a
 
 for TARGET in $TARGETS; do
     case $TARGET in
-    ""|--without-openssl|--without-zlib)
+    ""|--without-openssl|--without-zlib|--with-Werror)
         # nothing to do
         ;;
     "--with-kerberos5")

.github/workflows/c-cpp.yml

@@ -15,7 +15,7 @@ jobs:
       matrix:
         configs:
         - ""
-        - "--with-kerberos5 --with-libedit --with-pam --with-security-key-builtin --with-selinux"
+        - "--with-kerberos5 --with-libedit --with-pam --with-security-key-builtin --with-selinux --with-Werror"
         - "--with-ldflags=-lhardened_malloc"
 
     steps: