hunter: make ZLIB play nice with Hunter, cmake config

- Teach ZLIB respect `BUILD_SHARED_LIBS`
- Set version in command 'project'
- Use configure_package_config_file
- Install `ZLIBconfig.cmake`
- Add ZLIB::ZLIB ALIAS target

Author: olliwang

CMakeLists.txt

@@ -1,9 +1,9 @@
 cmake_minimum_required(VERSION 2.4.4...3.15.0)
 set(CMAKE_ALLOW_LOOSE_LOOP_CONSTRUCTS ON)
 
-project(zlib C)
+project(ZLIB VERSION "1.3.1" LANGUAGES C)
 
-set(VERSION "1.3.1")
+set(VERSION "${PROJECT_VERSION}")
 
 option(ZLIB_BUILD_EXAMPLES "Enable Zlib Examples" ON)
 
@@ -149,10 +149,7 @@ if(MINGW)
     set(ZLIB_DLL_SRCS ${CMAKE_CURRENT_BINARY_DIR}/zlib1rc.obj)
 endif(MINGW)
 
-add_library(zlib SHARED ${ZLIB_SRCS} ${ZLIB_DLL_SRCS} ${ZLIB_PUBLIC_HDRS} ${ZLIB_PRIVATE_HDRS})
-target_include_directories(zlib PUBLIC ${CMAKE_CURRENT_BINARY_DIR} ${CMAKE_CURRENT_SOURCE_DIR})
-add_library(zlibstatic STATIC ${ZLIB_SRCS} ${ZLIB_PUBLIC_HDRS} ${ZLIB_PRIVATE_HDRS})
-target_include_directories(zlibstatic PUBLIC ${CMAKE_CURRENT_BINARY_DIR} ${CMAKE_CURRENT_SOURCE_DIR})
+add_library(zlib ${ZLIB_SRCS} ${ZLIB_DLL_SRCS} ${ZLIB_PUBLIC_HDRS} ${ZLIB_PRIVATE_HDRS})
 set_target_properties(zlib PROPERTIES DEFINE_SYMBOL ZLIB_DLL)
 set_target_properties(zlib PROPERTIES SOVERSION 1)
 
@@ -169,7 +166,7 @@ endif()
 
 if(UNIX)
     # On unix-like platforms the library is almost always called libz
-   set_target_properties(zlib zlibstatic PROPERTIES OUTPUT_NAME z)
+   set_target_properties(zlib PROPERTIES OUTPUT_NAME z)
    if(NOT APPLE AND NOT(CMAKE_SYSTEM_NAME STREQUAL AIX))
      set_target_properties(zlib PROPERTIES LINK_FLAGS "-Wl,--version-script,\"${CMAKE_CURRENT_SOURCE_DIR}/zlib.map\"")
    endif()
@@ -178,11 +175,52 @@ elseif(BUILD_SHARED_LIBS AND WIN32)
     set_target_properties(zlib PROPERTIES SUFFIX "1.dll")
 endif()
 
-if(NOT SKIP_INSTALL_LIBRARIES AND NOT SKIP_INSTALL_ALL )
-    install(TARGETS zlib zlibstatic
-        RUNTIME DESTINATION "${INSTALL_BIN_DIR}"
-        ARCHIVE DESTINATION "${INSTALL_LIB_DIR}"
-        LIBRARY DESTINATION "${INSTALL_LIB_DIR}" )
+if(NOT SKIP_INSTALL_LIBRARIES AND NOT SKIP_INSTALL_ALL)
+  # Installation (https://github.com/forexample/package-example)
+
+  set(config_install_dir "lib/cmake/${PROJECT_NAME}")
+  set(include_install_dir "include")
+
+  set(generated_dir "${CMAKE_CURRENT_BINARY_DIR}/generated")
+
+  set(version_config "${generated_dir}/${PROJECT_NAME}ConfigVersion.cmake")
+  set(project_config "${generated_dir}/${PROJECT_NAME}Config.cmake")
+  set(targets_export_name "${PROJECT_NAME}Targets")
+  set(namespace "${PROJECT_NAME}::")
+
+  include(CMakePackageConfigHelpers)
+
+  # Note: PROJECT_VERSION is used as a VERSION
+  write_basic_package_version_file(
+      "${version_config}" COMPATIBILITY SameMajorVersion
+  )
+
+  # Note: variable 'targets_export_name' used
+  configure_package_config_file(
+      "cmake/Config.cmake.in"
+      "${project_config}"
+      INSTALL_DESTINATION "${config_install_dir}"
+  )
+
+  install(
+      TARGETS zlib
+      EXPORT "${targets_export_name}"
+      LIBRARY DESTINATION "lib"
+      ARCHIVE DESTINATION "lib"
+      RUNTIME DESTINATION "bin"
+      INCLUDES DESTINATION "${include_install_dir}"
+  )
+
+  install(
+      FILES "${project_config}" "${version_config}"
+      DESTINATION "${config_install_dir}"
+  )
+
+  install(
+      EXPORT "${targets_export_name}"
+      NAMESPACE "${namespace}"
+      DESTINATION "${config_install_dir}"
+  )
 endif()
 if(NOT SKIP_INSTALL_HEADERS AND NOT SKIP_INSTALL_ALL )
     install(FILES ${ZLIB_PUBLIC_HDRS} DESTINATION "${INSTALL_INC_DIR}")

cmake/Config.cmake.in

@@ -0,0 +1,13 @@
+@PACKAGE_INIT@
+
+include("${CMAKE_CURRENT_LIST_DIR}/@[email protected]")
+check_required_components("@PROJECT_NAME@")
+
+if(NOT TARGET ZLIB::ZLIB)
+  set_target_properties(
+      ZLIB::zlib
+      PROPERTIES
+      IMPORTED_GLOBAL True
+  )
+  add_library(ZLIB::ZLIB ALIAS ZLIB::zlib)
+endif()