meson: support building .standalone variants for shared modules

Extend the module building logic to automatically generate '.standalone'
variants for non-NSS/PAM shared modules (such as cryptsetup tokens).

Like standalone executables, these are not built by default to keep
the base build time unaffected, but can be built explicitly on demand
via `ninja <module_name>.standalone`.

src/cryptsetup/cryptsetup-tokens/meson.build

@@ -9,7 +9,6 @@ lib_cryptsetup_token_common = static_library(
                 libcryptsetup_cflags,
                 userspace,
         ],
-        link_with : libshared,
         build_by_default : false)
 
 cryptsetup_token_systemd_tpm2_sources = files(