enet: Update to 1.3.18 and clean up CMake

Our CMakeLists was more or less a copy/paste of the one from enet

Externals/enet/CMakeLists.txt

@@ -1,104 +1,5 @@
-cmake_minimum_required(VERSION 2.8.12)
-
-project(enet)
-
-# The "configure" step.
-include(CheckFunctionExists)
-include(CheckStructHasMember)
-include(CheckTypeSize)
-
-if(HAIKU)
-    set(CMAKE_REQUIRED_LIBRARIES network)
-endif(HAIKU)
-
-check_function_exists("fcntl" HAS_FCNTL)
-check_function_exists("poll" HAS_POLL)
-check_function_exists("getaddrinfo" HAS_GETADDRINFO)
-check_function_exists("getnameinfo" HAS_GETNAMEINFO)
-check_function_exists("gethostbyname_r" HAS_GETHOSTBYNAME_R)
-check_function_exists("gethostbyaddr_r" HAS_GETHOSTBYADDR_R)
-check_function_exists("inet_pton" HAS_INET_PTON)
-check_function_exists("inet_ntop" HAS_INET_NTOP)
-check_struct_has_member("struct msghdr" "msg_flags" "sys/types.h;sys/socket.h" HAS_MSGHDR_FLAGS)
-set(CMAKE_EXTRA_INCLUDE_FILES "sys/types.h" "sys/socket.h")
-check_type_size("socklen_t" HAS_SOCKLEN_T BUILTIN_TYPES_ONLY)
-unset(CMAKE_EXTRA_INCLUDE_FILES)
-
-if(HAIKU)
-    unset(CMAKE_REQUIRED_LIBRARIES)
-endif()
-
-if(HAS_FCNTL)
-    add_definitions(-DHAS_FCNTL=1)
-endif()
-if(HAS_POLL)
-    add_definitions(-DHAS_POLL=1)
-endif()
-if(HAS_GETNAMEINFO)
-    add_definitions(-DHAS_GETNAMEINFO=1)
-endif()
-if(HAS_GETADDRINFO)
-    add_definitions(-DHAS_GETADDRINFO=1)
-endif()
-if(HAS_GETHOSTBYNAME_R)
-    add_definitions(-DHAS_GETHOSTBYNAME_R=1)
-endif()
-if(HAS_GETHOSTBYADDR_R)
-    add_definitions(-DHAS_GETHOSTBYADDR_R=1)
-endif()
-if(HAS_INET_PTON)
-    add_definitions(-DHAS_INET_PTON=1)
-endif()
-if(HAS_INET_NTOP)
-    add_definitions(-DHAS_INET_NTOP=1)
-endif()
-if(HAS_MSGHDR_FLAGS)
-    add_definitions(-DHAS_MSGHDR_FLAGS=1)
-endif()
-if(HAS_SOCKLEN_T)
-    add_definitions(-DHAS_SOCKLEN_T=1)
-endif()
-
-set(INCLUDE_FILES_PREFIX enet/include/enet)
-set(INCLUDE_FILES
-    ${INCLUDE_FILES_PREFIX}/callbacks.h
-    ${INCLUDE_FILES_PREFIX}/enet.h
-    ${INCLUDE_FILES_PREFIX}/list.h
-    ${INCLUDE_FILES_PREFIX}/protocol.h
-    ${INCLUDE_FILES_PREFIX}/time.h
-    ${INCLUDE_FILES_PREFIX}/types.h
-    ${INCLUDE_FILES_PREFIX}/unix.h
-    ${INCLUDE_FILES_PREFIX}/utility.h
-    ${INCLUDE_FILES_PREFIX}/win32.h
-)
-
-set(SOURCE_FILES
-    enet/callbacks.c
-    enet/compress.c
-    enet/host.c
-    enet/list.c
-    enet/packet.c
-    enet/peer.c
-    enet/protocol.c
-    enet/unix.c
-    enet/win32.c)
-
-source_group(include FILES ${INCLUDE_FILES})
-source_group(source FILES ${SOURCE_FILES})
-
-add_library(enet STATIC
-    ${INCLUDE_FILES}
-    ${SOURCE_FILES}
-)
-target_include_directories(enet PUBLIC enet/include)
+add_subdirectory(enet)
 
 dolphin_disable_warnings(enet)
 add_library(enet::enet ALIAS enet)
-
-if (MINGW)
-    target_link_libraries(enet winmm ws2_32)
-endif()
-
-if(HAIKU)
-    target_link_libraries(enet network)
-endif(HAIKU)
+target_include_directories(enet PUBLIC enet/include)