gnu: gcl: Use 'modify-phases' syntax.

* gnu/packages/lisp.scm (gcl)[arguments]: Use 'modify-phases' syntax.

gnu/packages/lisp.scm

@@ -88,8 +88,8 @@
      `(#:parallel-build? #f  ; The build system seems not to be thread safe.
        #:tests? #f  ; There does not seem to be make check or anything similar.
        #:configure-flags '("--enable-ansi") ; required for use by the maxima package
-       #:phases (alist-cons-before
-                'configure 'pre-conf
+       #:phases (modify-phases %standard-phases
+                  (add-before 'configure 'pre-conf
                     (lambda _
                       (substitute*
                         (append
@@ -104,11 +104,10 @@
                          (string-append "SHELL=" (which "bash")))
                         (("SHELL=/bin/sh")
                          (string-append "SHELL=" (which "sh"))))
-                  #t)
+                      #t))
                   ;; drop strip phase to make maxima build, see
                   ;; https://www.ma.utexas.edu/pipermail/maxima/2008/009769.html
-                (alist-delete 'strip
-                 %standard-phases))))
+                  (delete 'strip))))
     (inputs
      `(("gmp" ,gmp)
        ("readline" ,readline)))