Brad is working on a newer Boost. He sent me this diff to fix the build

using this new Boost. It doesn't affect the build with the current Boost.
While here, sync PLIST (adds the new-ish @so markers).

games/returntotheroots/Makefile

@@ -1,11 +1,11 @@
-# $OpenBSD: Makefile,v 1.13 2020/08/15 20:30:56 rsadowski Exp $
+# $OpenBSD: Makefile,v 1.14 2020/12/12 06:59:51 bcallah Exp $
 
 V =		0.8.2.20180924
 COMMENT =	open source engine remake of The Settlers 2 (s25client)
 DISTNAME =	s25client-${V}
 PKGNAME =	returntotheroots-${V}
 CATEGORIES =	games x11
-REVISION =	3
+REVISION =	4
 
 ONLY_FOR_ARCHS =	i386 amd64
 

games/returntotheroots/patches/patch-libutil_src_System_cpp

@@ -0,0 +1,24 @@
+$OpenBSD: patch-libutil_src_System_cpp,v 1.1 2020/12/12 06:59:51 bcallah Exp $
+
+Fix build with newer Boost.
+
+Index: libutil/src/System.cpp
+--- libutil/src/System.cpp.orig
++++ libutil/src/System.cpp
+@@ -251,7 +251,6 @@ bfs::path System::getExecutablePath()
+ 
+ #undef AIX
+ #undef AMIGAOS
+-#undef ANDROID
+ #undef BEOS
+ #undef BSD
+ #undef CYGWIN
+@@ -271,7 +270,7 @@ bfs::path System::getExecutablePath()
+ #undef BSD_NET
+ #undef BSD_OPEN
+ #define RTTR_BOOST_OS_LIST                                                                                                         \
+-    (AIX)(AMIGAOS)(ANDROID)(BEOS)(BSD)(CYGWIN)(HPUX)(IRIX)(LINUX)(MACOS)(OS400)(QNX)(SOLARIS)(UNIX)(SVR4)(VMS)(WINDOWS)(BSD_BSDI)( \
++    (AIX)(AMIGAOS)(BEOS)(BSD)(CYGWIN)(HPUX)(IRIX)(LINUX)(MACOS)(OS400)(QNX)(SOLARIS)(UNIX)(SVR4)(VMS)(WINDOWS)(BSD_BSDI)( \
+       BSD_DRAGONFLY)(BSD_FREE)(BSD_NET)(BSD_OPEN)
+ 
+ #undef BORLAND

games/returntotheroots/pkg/PLIST

@@ -1,11 +1,11 @@
-@comment $OpenBSD: PLIST,v 1.4 2018/09/04 12:46:13 espie Exp $
+@comment $OpenBSD: PLIST,v 1.5 2020/12/12 06:59:52 bcallah Exp $
 @bin bin/s25client
 @bin bin/s25edit
 lib/driver/
 lib/driver/audio/
-lib/driver/audio/libaudioSDL.so
+@so lib/driver/audio/libaudioSDL.so
 lib/driver/video/
-lib/driver/video/libvideoSDL.so
+@so lib/driver/video/libvideoSDL.so
 libexec/s25rttr/
 @bin libexec/s25rttr/s-c_resample
 @bin libexec/s25rttr/sound-convert