gnu: sed: Allow cross-compilation.

* gnu/packages/base.scm (sed): Keep the default phases
  when (%current-target-system) is true.

gnu/packages/base.scm

@@ -101,6 +101,8 @@ lines.")
    (build-system gnu-build-system)
    (synopsis "Stream editor")
    (arguments
+    (if (%current-target-system)
+        '()
         `(#:phases (alist-cons-before
                     'patch-source-shebangs 'patch-test-suite
                     (lambda* (#:key inputs #:allow-other-keys)
@@ -110,7 +112,7 @@ lines.")
                                        "testsuite/bug-regex9.c")
                           (("/bin/sh")
                            (string-append bash "/bin/bash")))))
-                %standard-phases)))
+                    %standard-phases))))
    (description
     "Sed (stream editor) isn't really a true text editor or text processor.
 Instead, it is used to filter text, i.e., it takes text input and performs