lzma is p7zip not liblzma
--- src/External/CMakeLists.txt
+++ src/External/CMakeLists.txt
@@ -24,12 +24,10 @@
 file(GLOB_RECURSE EXTERNAL_SOURCES
 	*.cpp
 	*.cxx
-	dumb/*.c
-	lua/*.c
 	lzma/C/LzmaDec.c
 	${SLADE_HEADERS}
 	)
 
 add_library(external STATIC ${EXTERNAL_SOURCES})
 target_link_libraries(external ${ZLIB_LIBRARY})
-set(EXTERNAL_LIBRARIES external PARENT_SCOPE)
+set(EXTERNAL_LIBRARIES external dumb lua5.3 PARENT_SCOPE)