libsystemd: link with '-z nodelete'

We want to avoid reinitialization of our global variables with static
storage duration in case we get dlopened multiple times by the same
application. This will avoid potential resource leaks that could have
happened otherwise (e.g. leaking journal socket fd).

(cherry picked from commit 9d8533b)

Resolves: RHEL-6589

meson.build

@@ -2004,6 +2004,8 @@ libsystemd = shared_library(
         version : libsystemd_version,
         include_directories : libsystemd_includes,
         link_args : ['-shared',
+                     # Make sure our library is never deleted from memory, so that our open logging fds don't leak on dlopen/dlclose cycles.
+                     '-z', 'nodelete',
                      '-Wl,--version-script=' + libsystemd_sym_path],
         link_with : [libbasic,
                      libbasic_gcrypt,