Use full RELRO for modules (use HARDEN_LDFLAGS in MODULEFLAGS)

Previously, due to HARDEN_LDFLAGS missing in MODULEFLAGS we were
only partial RELRO instead of full RELRO. This is a defense-in-
depth measure but is good to have and the ommission was unintended.

configure

@@ -8266,7 +8266,7 @@ printf "%s\n" "#define UNDERSCORE /**/" >>confdefs.h
 
 fi
 
-MODULEFLAGS="$ac_cv_pic $DYNAMIC_LDFLAGS"
+MODULEFLAGS="$ac_cv_pic $DYNAMIC_LDFLAGS $HARDEN_LDFLAGS"
 
 else case e in #(
   e)

configure.ac

@@ -349,7 +349,7 @@ if test "$ac_cv_underscore" = "yes"; then
 	AC_DEFINE([UNDERSCORE], [], [Define if your system prepends an underscore to symbols])
 fi
 
-MODULEFLAGS="$ac_cv_pic $DYNAMIC_LDFLAGS"
+MODULEFLAGS="$ac_cv_pic $DYNAMIC_LDFLAGS $HARDEN_LDFLAGS"
 dnl DYNAMIC_LINKING is not meant to be defined in include/setup.h, it's 
 dnl defined in the Makefiles using -D. Having it defined globally will
 dnl only cause braindamage and symbol collisions :-D.

doc/RELEASE-NOTES.md

@@ -30,6 +30,8 @@ This version comes with a few enhancements and has quite a number of bugfixes.
   [set::handshake-timeout](https://www.unrealircd.org/docs/Set_block#set::handshake-timeout)
   from 30 to 40 seconds.
 * Update shipped libs: PCRE2 (10.47), Jansson (2.15.0), Sodium (1.0.21)
+* Minor hardening tweak for modules, reducing the impact of some security bugs
+  (full RELRO instead of partial RELRO)
 
 ### Fixes:
 * Crash when using [Extended Server Bans](https://www.unrealircd.org/docs/Extended_server_bans)