gnu: Add sbcl-usocket-boot0.

* gnu/packages/lisp.scm (sbcl-usocket-boot0): New variable.

gnu/packages/lisp.scm

@@ -3592,3 +3592,34 @@ Lisp (from GBBopen project).")
 
 (define-public ecl-portable-threada
   (sbcl-package->ecl-package sbcl-portable-threads))
+
+(define-public sbcl-usocket-boot0
+  ;; usocket's test rely on usocket-server which depends on usocket itself.
+  ;; We break this cyclic dependency with -boot0 that packages usocket.
+  (let ((commit "86e7efbfe50101931edf4b67cdcfa7e221ecfde9"))
+    (package
+      (name "sbcl-usocket-boot0")
+      (version (git-version "0.7.1" "1" commit))
+      (source
+       (origin
+         (method git-fetch)
+         (uri (git-reference
+               (url "https://github.com/usocket/usocket/")
+               (commit commit)))
+         (file-name (git-file-name "usocket" version))
+         (sha256
+          (base32
+           "1lk6ipakrib7kdgzw44hrgmls9akp5pz4h35yynw0k5zwmmq6374"))))
+      (build-system asdf-build-system/sbcl)
+      (inputs
+       `(("split-sequence" ,sbcl-split-sequence)))
+      (arguments
+       `(#:tests? #f
+         #:asd-system-name "usocket"))
+      (home-page "https://common-lisp.net/project/usocket/")
+      (synopsis "Universal socket library for Common Lisp (server side)")
+      (description
+       "This library strives to provide a portable TCP/IP and UDP/IP socket
+interface for as many Common Lisp implementations as possible, while keeping
+the abstraction and portability layer as thin as possible.")
+      (license license:expat))))