Include version symbols for cmake builds.

Add a version variable so it gets added to the pkg-config file.

CMakeLists.txt

@@ -3,6 +3,8 @@ set(CMAKE_ALLOW_LOOSE_LOOP_CONSTRUCTS ON)
 
 project(zlib C)
 
+set(VERSION "1.2.7")
+
 set(INSTALL_BIN_DIR "${CMAKE_INSTALL_PREFIX}/bin" CACHE PATH "Installation directory for executables")
 set(INSTALL_LIB_DIR "${CMAKE_INSTALL_PREFIX}/lib" CACHE PATH "Installation directory for libraries")
 set(INSTALL_INC_DIR "${CMAKE_INSTALL_PREFIX}/include" CACHE PATH "Installation directory for headers")
@@ -162,6 +164,7 @@ 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 LINK_FLAGS "-Wl,--version-script,zlib.map")
 elseif(BUILD_SHARED_LIBS AND WIN32)
     # Creates zlib1.dll when building shared library version
     set_target_properties(zlib PROPERTIES SUFFIX "1.dll")