coreutils: fix test suite

* gnu/packages/patches/coreutils-skip-nohup.patch: patch taken from the git
  repository of coreutils, that makes sure tests/misc/nohup.sh does not fail
  when /dev/tty does not exist.
* gnu/packages/base.scm (coreutils): use it.
* gnu-system.am (dist_patch_DATA): add it.

gnu-system.am

@@ -252,6 +252,7 @@ dist_patch_DATA =						\
   gnu/packages/patches/cdparanoia-fpic.patch			\
   gnu/packages/patches/cmake-fix-tests.patch			\
   gnu/packages/patches/coreutils-dummy-man.patch		\
+  gnu/packages/patches/coreutils-skip-nohup.patch		\
   gnu/packages/patches/cpio-gets-undeclared.patch		\
   gnu/packages/patches/curl-fix-test172.patch			\
   gnu/packages/patches/dbus-localstatedir.patch			\

gnu/packages/base.scm

@@ -240,7 +240,9 @@ used to apply commands with arbitrarily long arguments.")
             (sha256
              (base32
               "04hjzzv434fb8ak3hh3dyhdvg3hqjjwvjmjxqzk1gh2jh6cr8gjv"))
-            (patches (list (search-patch "coreutils-dummy-man.patch")))))
+            (patches (list (search-patch "coreutils-dummy-man.patch")
+                           ;; TODO: remove this patch for >= 8.23
+                           (search-patch "coreutils-skip-nohup.patch")))))
    (build-system gnu-build-system)
    (inputs `(("acl"  ,acl)                        ; TODO: add SELinux
              ("gmp"  ,gmp)))

gnu/packages/patches/coreutils-skip-nohup.patch

@@ -0,0 +1,28 @@
+commit 5dce6bdfafc930dfd17d5d16aea7d1add3472066
+Author: Pádraig Brady <P@draigBrady.com>
+Date:   Wed Mar 5 15:14:07 2014 +0000
+
+    tests: fix false failure in nohup.sh in non tty builds
+    
+    * tests/misc/nohup.sh: When running tests without a controlling tty,
+    an exec failure is triggered in a subshell, which causes POSIX
+    shells to immediately exit the subshell.  This was brought
+    to notice by the newly conforming bash 4.3.
+    Fixes http:/bugs.gnu.org/16940
+
+diff --git a/tests/misc/nohup.sh b/tests/misc/nohup.sh
+index 6d2b515..2328b43 100755
+--- a/tests/misc/nohup.sh
++++ b/tests/misc/nohup.sh
+@@ -63,6 +63,11 @@ rm -f nohup.out err
+ # to stderr must be fatal.  Requires stdout to be terminal.
+ if test -w /dev/full && test -c /dev/full; then
+ (
++  # POSIX shells immediately exit the subshell on exec error.
++  # So check we can write to /dev/tty before the exec, which
++  # isn't possible if we've no controlling tty for example.
++  test -c /dev/tty && >/dev/tty || exit 0
++
+   exec >/dev/tty
+   test -t 1 || exit 0
+   nohup echo hi 2> /dev/full