gnu: smalltalk: Use 'inputs' in phases instead of '%build-inputs'.

In build phases, the former is preferred.

* gnu/packages/smalltalk.scm
  (smalltalk)[arguments]<#:phases>{fix-libc}: Use 'inputs'
  argument instead of '%build-inputs'.

Signed-off-by: Mathieu Othacehe <othacehe@gnu.org>

gnu/packages/smalltalk.scm

@@ -102,8 +102,8 @@
                        (find-files "doc" "\\.info"))
              #t))
          (add-before 'configure 'fix-libc
-           (lambda _
-             (let ((libc (assoc-ref %build-inputs "libc")))
+           (lambda* (#:key inputs #:allow-other-keys)
+             (let ((libc (assoc-ref inputs "libc")))
                (substitute* "libc.la.in"
                  (("@LIBC_SO_NAME@") "libc.so")
                  (("@LIBC_SO_DIR@")  (string-append libc "/lib"))))