Build cctz as part of znclib when not found

Because on cygwin otherwise it would be a separate dll

CMakeLists.txt

@@ -272,23 +272,24 @@ endif()
 # TODO: verify that this find_package works; on Gentoo it's not currently (Jan
 # 2023) packaged, so in my tests it always falls back to submodule
 find_package(cctz QUIET)
+set(cctz_cc "")
 if (NOT cctz_FOUND)
 	set(cctz_cc
-		third_party/cctz/src/civil_time_detail.cc
-		third_party/cctz/src/time_zone_fixed.cc
-		third_party/cctz/src/time_zone_format.cc
-		third_party/cctz/src/time_zone_if.cc
-		third_party/cctz/src/time_zone_impl.cc
-		third_party/cctz/src/time_zone_info.cc
-		third_party/cctz/src/time_zone_libc.cc
-		third_party/cctz/src/time_zone_lookup.cc
-		third_party/cctz/src/time_zone_posix.cc
-		third_party/cctz/src/zone_info_source.cc
+		${PROJECT_SOURCE_DIR}/third_party/cctz/src/civil_time_detail.cc
+		${PROJECT_SOURCE_DIR}/third_party/cctz/src/time_zone_fixed.cc
+		${PROJECT_SOURCE_DIR}/third_party/cctz/src/time_zone_format.cc
+		${PROJECT_SOURCE_DIR}/third_party/cctz/src/time_zone_if.cc
+		${PROJECT_SOURCE_DIR}/third_party/cctz/src/time_zone_impl.cc
+		${PROJECT_SOURCE_DIR}/third_party/cctz/src/time_zone_info.cc
+		${PROJECT_SOURCE_DIR}/third_party/cctz/src/time_zone_libc.cc
+		${PROJECT_SOURCE_DIR}/third_party/cctz/src/time_zone_lookup.cc
+		${PROJECT_SOURCE_DIR}/third_party/cctz/src/time_zone_posix.cc
+		${PROJECT_SOURCE_DIR}/third_party/cctz/src/zone_info_source.cc
 	)
-	add_library(cctz STATIC EXCLUDE_FROM_ALL ${cctz_cc})
+	add_library(cctz INTERFACE EXCLUDE_FROM_ALL)
 	add_library(cctz::cctz ALIAS cctz)
-	target_include_directories(cctz PUBLIC
-		${PROJECT_SOURCE_DIR}/third_party/cctz/include)
+	target_include_directories(cctz INTERFACE
+		$<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/third_party/cctz/include>)
 endif()
 
 check_cxx_symbol_exists(getopt_long "getopt.h" HAVE_GETOPT_LONG)

src/CMakeLists.txt

@@ -25,7 +25,8 @@ set(znc_cpp "ZNCString.cpp" "znc.cpp" "IRCNetwork.cpp" "Translation.cpp"
 	"HTTPSock.cpp" "Template.cpp" "ClientCommand.cpp" "Socket.cpp"
 	"SHA256.cpp" "WebModules.cpp" "Listener.cpp" "Config.cpp" "ZNCDebug.cpp"
 	"Threads.cpp" "Query.cpp" "SSLVerifyHost.cpp" "Message.cpp" "User.cpp")
-znc_add_library(znclib ${lib_type} ${znc_cpp} "Csocket.cpp" "versionc.cpp")
+znc_add_library(znclib ${lib_type} ${znc_cpp} "Csocket.cpp" "versionc.cpp"
+	${cctz_cc})
 znc_add_executable(znc "main.cpp")
 target_link_libraries(znc PRIVATE znclib)