cmake: add support for transitive ZLIB target

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1867a43025cc1e16921df97b98d6a6af51a4a63b..0478ae17959c3bf95754261993a4c932bee8ee2d 100644 (file)
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -515,8 +515,16 @@ if(CURL_ZLIB)
     set(HAVE_ZLIB_H ON)
     set(HAVE_ZLIB ON)
     set(HAVE_LIBZ ON)
-    list(APPEND CURL_LIBS ${ZLIB_LIBRARIES})
-    include_directories(${ZLIB_INCLUDE_DIRS})
+
+    # Depend on ZLIB via imported targets if supported by the running
+    # version of CMake.  This allows our dependents to get our dependencies
+    # transitively.
+    if(NOT CMAKE_VERSION VERSION_LESS 3.4)
+      list(APPEND CURL_LIBS ZLIB::ZLIB)
+    else()
+      list(APPEND CURL_LIBS ${ZLIB_LIBRARIES})
+      include_directories(${ZLIB_INCLUDE_DIRS})
+    endif()
     list(APPEND CMAKE_REQUIRED_INCLUDES ${ZLIB_INCLUDE_DIRS})
   endif()
 endif()