Un-break AIX build, take 2.

I incorrectly diagnosed the reason why hoverfly is unhappy.
Looking closer, it appears that it fails to link libldap
unless libssl is also present; so the problem was my
idea of clearing LIBS before making the check.  Revert
to essentially the original coding, except that instead
of failing when libldap_r isn't there, use libldap.

Per buildfarm member hoverfly.

Discussion: https://postgr.es/m/17083-a19190d9591946a7@postgresql.org

configure

@@ -12876,22 +12876,18 @@ fi
 
 fi
 
-# Note: We can test for libldap_r only after we know PTHREAD_LIBS
+# Note: We can test for libldap_r only after we know PTHREAD_LIBS;
+# also, on AIX, we may need to have openssl in LIBS for this step.
 if test "$with_ldap" = yes ; then
   _LIBS="$LIBS"
   if test "$PORTNAME" != "win32"; then
-    if test "$enable_thread_safety" = yes; then
-      # Use ldap_r for FE if available, else assume ldap is thread-safe.
-      # If ldap_r does exist, assume without checking that ldap does too.
-      # On some platforms ldap_r fails to link without PTHREAD_LIBS;
-      # also, on AIX we must probe ldap_simple_bind not ldap_bind.
-      LIBS=""
-      { $as_echo "$as_me:${as_lineno-$LINENO}: checking for library containing ldap_simple_bind" >&5
-$as_echo_n "checking for library containing ldap_simple_bind... " >&6; }
-if ${ac_cv_search_ldap_simple_bind+:} false; then :
+    { $as_echo "$as_me:${as_lineno-$LINENO}: checking for ldap_bind in -lldap" >&5
+$as_echo_n "checking for ldap_bind in -lldap... " >&6; }
+if ${ac_cv_lib_ldap_ldap_bind+:} false; then :
   $as_echo_n "(cached) " >&6
 else
-  ac_func_search_save_LIBS=$LIBS
+  ac_check_lib_save_LIBS=$LIBS
+LIBS="-lldap $EXTRA_LDAP_LIBS $LIBS"
 cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 
@@ -12901,59 +12897,49 @@ cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 #ifdef __cplusplus
 extern "C"
 #endif
-char ldap_simple_bind ();
+char ldap_bind ();
 int
 main ()
 {
-return ldap_simple_bind ();
+return ldap_bind ();
   ;
   return 0;
 }
 _ACEOF
-for ac_lib in '' ldap_r ldap; do
-  if test -z "$ac_lib"; then
-    ac_res="none required"
-  else
-    ac_res=-l$ac_lib
-    LIBS="-l$ac_lib $PTHREAD_CFLAGS $PTHREAD_LIBS $EXTRA_LDAP_LIBS $ac_func_search_save_LIBS"
-  fi
-  if ac_fn_c_try_link "$LINENO"; then :
-  ac_cv_search_ldap_simple_bind=$ac_res
+if ac_fn_c_try_link "$LINENO"; then :
+  ac_cv_lib_ldap_ldap_bind=yes
+else
+  ac_cv_lib_ldap_ldap_bind=no
 fi
 rm -f core conftest.err conftest.$ac_objext \
-    conftest$ac_exeext
-  if ${ac_cv_search_ldap_simple_bind+:} false; then :
-  break
+    conftest$ac_exeext conftest.$ac_ext
+LIBS=$ac_check_lib_save_LIBS
 fi
-done
-if ${ac_cv_search_ldap_simple_bind+:} false; then :
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_lib_ldap_ldap_bind" >&5
+$as_echo "$ac_cv_lib_ldap_ldap_bind" >&6; }
+if test "x$ac_cv_lib_ldap_ldap_bind" = xyes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_LIBLDAP 1
+_ACEOF
 
-else
-  ac_cv_search_ldap_simple_bind=no
-fi
-rm conftest.$ac_ext
-LIBS=$ac_func_search_save_LIBS
-fi
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_search_ldap_simple_bind" >&5
-$as_echo "$ac_cv_search_ldap_simple_bind" >&6; }
-ac_res=$ac_cv_search_ldap_simple_bind
-if test "$ac_res" != no; then :
-  test "$ac_res" = "none required" || LIBS="$ac_res $LIBS"
+  LIBS="-lldap $LIBS"
 
 else
   as_fn_error $? "library 'ldap' is required for LDAP" "$LINENO" 5
 fi
 
-      LDAP_LIBS_FE="$LIBS $EXTRA_LDAP_LIBS"
     LDAP_LIBS_BE="-lldap $EXTRA_LDAP_LIBS"
-    else
-      { $as_echo "$as_me:${as_lineno-$LINENO}: checking for ldap_bind in -lldap" >&5
-$as_echo_n "checking for ldap_bind in -lldap... " >&6; }
-if ${ac_cv_lib_ldap_ldap_bind+:} false; then :
+    if test "$enable_thread_safety" = yes; then
+      # Use ldap_r for FE if available, else assume ldap is thread-safe.
+      # On some platforms ldap_r fails to link without PTHREAD_LIBS.
+      LIBS="$_LIBS"
+      { $as_echo "$as_me:${as_lineno-$LINENO}: checking for ldap_bind in -lldap_r" >&5
+$as_echo_n "checking for ldap_bind in -lldap_r... " >&6; }
+if ${ac_cv_lib_ldap_r_ldap_bind+:} false; then :
   $as_echo_n "(cached) " >&6
 else
   ac_check_lib_save_LIBS=$LIBS
-LIBS="-lldap $EXTRA_LDAP_LIBS $LIBS"
+LIBS="-lldap_r $PTHREAD_CFLAGS $PTHREAD_LIBS $EXTRA_LDAP_LIBS $LIBS"
 cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 
@@ -12973,29 +12959,24 @@ return ldap_bind ();
 }
 _ACEOF
 if ac_fn_c_try_link "$LINENO"; then :
-  ac_cv_lib_ldap_ldap_bind=yes
+  ac_cv_lib_ldap_r_ldap_bind=yes
 else
-  ac_cv_lib_ldap_ldap_bind=no
+  ac_cv_lib_ldap_r_ldap_bind=no
 fi
 rm -f core conftest.err conftest.$ac_objext \
     conftest$ac_exeext conftest.$ac_ext
 LIBS=$ac_check_lib_save_LIBS
 fi
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_lib_ldap_ldap_bind" >&5
-$as_echo "$ac_cv_lib_ldap_ldap_bind" >&6; }
-if test "x$ac_cv_lib_ldap_ldap_bind" = xyes; then :
-  cat >>confdefs.h <<_ACEOF
-#define HAVE_LIBLDAP 1
-_ACEOF
-
-  LIBS="-lldap $LIBS"
-
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_lib_ldap_r_ldap_bind" >&5
+$as_echo "$ac_cv_lib_ldap_r_ldap_bind" >&6; }
+if test "x$ac_cv_lib_ldap_r_ldap_bind" = xyes; then :
+  LDAP_LIBS_FE="-lldap_r $EXTRA_LDAP_LIBS"
 else
-  as_fn_error $? "library 'ldap' is required for LDAP" "$LINENO" 5
+  LDAP_LIBS_FE="-lldap $EXTRA_LDAP_LIBS"
 fi
 
+    else
       LDAP_LIBS_FE="-lldap $EXTRA_LDAP_LIBS"
-      LDAP_LIBS_BE="-lldap $EXTRA_LDAP_LIBS"
     fi
     for ac_func in ldap_initialize
 do :

configure.ac

@@ -1285,27 +1285,25 @@ if test "$with_lz4" = yes ; then
   AC_CHECK_LIB(lz4, LZ4_compress_default, [], [AC_MSG_ERROR([library 'lz4' is required for LZ4 support])])
 fi
 
-# Note: We can test for libldap_r only after we know PTHREAD_LIBS
+# Note: We can test for libldap_r only after we know PTHREAD_LIBS;
+# also, on AIX, we may need to have openssl in LIBS for this step.
 if test "$with_ldap" = yes ; then
   _LIBS="$LIBS"
   if test "$PORTNAME" != "win32"; then
+    AC_CHECK_LIB(ldap, ldap_bind, [],
+		 [AC_MSG_ERROR([library 'ldap' is required for LDAP])],
+		 [$EXTRA_LDAP_LIBS])
+    LDAP_LIBS_BE="-lldap $EXTRA_LDAP_LIBS"
     if test "$enable_thread_safety" = yes; then
       # Use ldap_r for FE if available, else assume ldap is thread-safe.
-      # If ldap_r does exist, assume without checking that ldap does too.
-      # On some platforms ldap_r fails to link without PTHREAD_LIBS;
-      # also, on AIX we must probe ldap_simple_bind not ldap_bind.
-      LIBS=""
-      AC_SEARCH_LIBS(ldap_simple_bind, [ldap_r ldap], [],
-                     [AC_MSG_ERROR([library 'ldap' is required for LDAP])],
+      # On some platforms ldap_r fails to link without PTHREAD_LIBS.
+      LIBS="$_LIBS"
+      AC_CHECK_LIB(ldap_r, ldap_bind,
+		   [LDAP_LIBS_FE="-lldap_r $EXTRA_LDAP_LIBS"],
+		   [LDAP_LIBS_FE="-lldap $EXTRA_LDAP_LIBS"],
 		   [$PTHREAD_CFLAGS $PTHREAD_LIBS $EXTRA_LDAP_LIBS])
-      LDAP_LIBS_FE="$LIBS $EXTRA_LDAP_LIBS"
-      LDAP_LIBS_BE="-lldap $EXTRA_LDAP_LIBS"
     else
-      AC_CHECK_LIB(ldap, ldap_bind, [],
-                   [AC_MSG_ERROR([library 'ldap' is required for LDAP])],
-                   [$EXTRA_LDAP_LIBS])
       LDAP_LIBS_FE="-lldap $EXTRA_LDAP_LIBS"
-      LDAP_LIBS_BE="-lldap $EXTRA_LDAP_LIBS"
     fi
     AC_CHECK_FUNCS([ldap_initialize])
   else