Link readline and zlib where MEGAcmd calls them directly.

megacmdshell.cpp (mega-cmd) calls readline(), add_history() and friends,
and megacmd_rotating_logger.cpp (mega-cmd-server) calls gzputs() and
friends. Neither target links the library: readline reaches them only
through SDKlib's private link interface, and zlib not at all, so the
links fail.

diff --git a/build/cmake/modules/megacmd_libraries.cmake b/build/cmake/modules/megacmd_libraries.cmake
index 59f9acb..9a2ad63 100644
--- a/build/cmake/modules/megacmd_libraries.cmake
+++ b/build/cmake/modules/megacmd_libraries.cmake
@@ -20,6 +20,12 @@ macro(load_megacmdserver_libraries)
             target_link_libraries(LMegacmdServer PRIVATE PkgConfig::pcre)
             set(USE_PCRE 1)
         endif()
+
+        pkg_check_modules(readline REQUIRED IMPORTED_TARGET readline)
+        target_link_libraries(mega-cmd PRIVATE PkgConfig::readline)
+
+        pkg_check_modules(zlib REQUIRED IMPORTED_TARGET zlib)
+        target_link_libraries(LMegacmdServer PRIVATE PkgConfig::zlib)
     endif()
 
 endmacro()