$ guix environment --ad-hoc guile2.2-gnutls
$ echo $GUILE_LOAD_PATH                    
/gnu/store/l2paa4ka8lglar0b778qzl7a6h2v5dzn-guile-json-0.6.0/share/guile/site/2.2:/gnu/store/babsf277js933gdk56a6mxiv8q80xiv4-guile-ssh-0.11.0/share/guile/site/2.2:/gnu/store/p28p47xxp67snmg46j5b1lkrj7hz27jj-guile2.2-gnutls-3.5.9/share/guile/site/2.2
$ guix build hello
substitute: guix substitute: warning: ACL for archive imports seems to be uninitialized, substitutes may be unavailable
substitute: ;;; Failed to autoload make-session in (gnutls):
substitute: ;;; ERROR: missing interface for module (gnutls)
substitute: Backtrace:
substitute:            1 (primitive-load "/home/leo/work/guix/scripts/guix")
substitute: In guix/ui.scm:
substitute:   1351:12  0 (run-guix-command _ . _)
substitute: 
substitute: guix/ui.scm:1351:12: In procedure run-guix-command:
substitute: guix/ui.scm:1351:12: In procedure module-lookup: Unbound variable: make-session
guix build: error: build failed: substituter `substitute' died unexpectedly