build: find/link readline for upnpctrl

Change-Id: I8a3adaea1827e79340955a4859ce76f621367888
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 900be4e..5268775 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -231,6 +231,12 @@
     target_include_directories(dnc PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/tools)
     install(TARGETS dsh RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR})
 
+    find_library(READLINE_LIBRARIES readline)
+    find_path(READLINE_INCLUDE_DIR readline/readline.h)
+    add_library(readline STATIC IMPORTED)
+    set_target_properties(readline PROPERTIES
+        IMPORTED_LOCATION "${READLINE_LIBRARIES}"
+        INTERFACE_INCLUDE_DIRECTORIES "${READLINE_INCLUDE_DIR}")
     add_executable(upnpctrl
         tools/upnp/upnpctrl.cpp)
     target_link_libraries(upnpctrl PRIVATE dhtnet fmt::fmt readline)