Sorry, this was missed. arx-libertatis uses boost (headerfiles only).
The following diff should fix this.
Index: Makefile
===================================================================
RCS file: /cvs/ports/games/arx-libertatis/Makefile,v
retrieving revision 1.1.1.1
diff -u -p -r1.1.1.1 Makefile
--- Makefile 6 May 2018 15:15:00 -0000 1.1.1.1
+++ Makefile 8 May 2018 18:11:28 -0000
@@ -9,6 +9,7 @@ GH_ACCOUNT = arx
GH_PROJECT = ArxLibertatis
GH_TAGNAME = 1.1.2-r1
PKGNAME = arx-libertatis-${GH_TAGNAME:S/-r/pl/}
+REVISION = 0
# GPLv3+, fonts are SIL OFL 1.1 license
PERMIT_PACKAGE_CDROM = Yes
@@ -21,6 +22,7 @@ COMPILER = base-clang ports-gcc ports-cl
MODULES = devel/cmake
+BUILD_DEPENDS = devel/boost>=1.48
LIB_DEPENDS = audio/openal \
devel/sdl \
graphics/glew
