gnu: gambit-c: Update to 4.9.0.

The tests makefile still contains the offending lines, but I was unable
to reproduce the failure across 3 different machines.

* gnu/packages/scheme.scm (gambit-c): Update to 4.9.0.
[arguments]: Remove 'fix-tests' phase.

gnu/packages/scheme.scm

@@ -532,7 +532,7 @@ of libraries.")
 (define-public gambit-c
   (package
     (name "gambit-c")
-    (version "4.8.9")
+    (version "4.9.0")
     (source
      (origin
        (method url-fetch)
@@ -542,24 +542,13 @@ of libraries.")
              (string-map (lambda (c) (if (char=? c #\.) #\_ c)) version)
              ".tgz"))
        (sha256
-        (base32 "16sg1s8myzxqpimj5ry6lfza0qfs157zj28bvmxwwgy89jd9m5v7"))))
+        (base32 "19862w9ij0g5xrkskl4g89xbs17gp9cc6cfcdca6dlfkb3lk6xhp"))))
     (build-system gnu-build-system)
     (arguments
      '(#:configure-flags
        ;; According to the ./configure script, this makes the build slower and
        ;; use >= 1 GB memory, but makes Gambit much faster.
-       '("--enable-single-host")
-       #:phases
-       (modify-phases %standard-phases
-         (add-before 'check 'fix-tests
-           (lambda _
-             (substitute* '("tests/makefile")
-               ;; '-:' is how run-time options are set.  'tl' sets some terminal
-               ;; option, which makes it fail in our build environment.  It
-               ;; recommends using 'd-' as a solution, which sets the REPL
-               ;; interaction channel to stdin/stdout.
-               (("gsi -:tl") "gsi -:d-,tl"))
-             #t)))))
+       '("--enable-single-host")))
     (home-page "http://gambitscheme.org")
     (synopsis "Efficient Scheme interpreter and compiler")
     (description