gnu: Add missing module to (gnu packages base).

This is a follow-up to commit 42958b5e0f.

Reported by pmikkelsen on IRC.

* gnu/packages/base.scm: Use srfi-1 for alist-delete.

gnu/packages/base.scm

@@ -53,6 +53,7 @@
   #:use-module (guix build-system gnu)
   #:use-module (guix build-system trivial)
   #:use-module (ice-9 match)
+  #:use-module (srfi srfi-1)
   #:export (glibc
             libiconv-if-needed))