Quote --version-script argument in CMakeLists.txt.

Previously, spaces in ${CMAKE_CURRENT_SOURCE_PATH} would expand into
multiple linker arguments.
diff --git a/CMakeLists.txt b/CMakeLists.txt
index cbb3d4c..0a4d54a 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -166,7 +166,7 @@
 if(UNIX)
     # On unix-like platforms the library is almost always called libz
    set_target_properties(zlib zlibstatic PROPERTIES OUTPUT_NAME z)
-   set_target_properties(zlib PROPERTIES LINK_FLAGS "-Wl,--version-script,${CMAKE_CURRENT_SOURCE_DIR}/zlib.map")
+   set_target_properties(zlib PROPERTIES LINK_FLAGS "-Wl,--version-script,\"${CMAKE_CURRENT_SOURCE_DIR}/zlib.map\"")
 elseif(BUILD_SHARED_LIBS AND WIN32)
     # Creates zlib1.dll when building shared library version
     set_target_properties(zlib PROPERTIES SUFFIX "1.dll")