gnu: gmp: Skip unreliable test.

* gnu/packages/patches/gmp-faulty-test.patch: New file.
* gnu-system.am (dist_patch_DATA): Add it.
* gnu/packages/multiprecision.scm (gmp)[source]: Use it.

gnu-system.am

@@ -474,6 +474,7 @@ dist_patch_DATA =						\
   gnu/packages/patches/glibc-o-largefile.patch			\
   gnu/packages/patches/glibc-versioned-locpath.patch		\
   gnu/packages/patches/gmp-arm-asm-nothumb.patch		\
+  gnu/packages/patches/gmp-faulty-test.patch			\
   gnu/packages/patches/gnucash-price-quotes-perl.patch		\
   gnu/packages/patches/gnutls-doc-fix.patch			\
   gnu/packages/patches/gobject-introspection-absolute-shlib-path.patch \

gnu/packages/multiprecision.scm

@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2012, 2013 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2012, 2013, 2015 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2014 Mark H Weaver <mhw@netris.org>
 ;;; Copyright © 2015 Andreas Enge <andreas@enge.fr>
 ;;;
@@ -39,7 +39,9 @@
             (sha256
              (base32
               "0r5pp27cy7ch3dg5v0rsny8bib1zfvrza6027g2mp5f6v8pd6mli"))
-            (patches (list (search-patch "gmp-arm-asm-nothumb.patch")))))
+            (patches (map search-patch
+                          '("gmp-arm-asm-nothumb.patch"
+                            "gmp-faulty-test.patch")))))
    (build-system gnu-build-system)
    (native-inputs `(("m4" ,m4)))
    (outputs '("out" "debug"))

gnu/packages/patches/gmp-faulty-test.patch

@@ -0,0 +1,11 @@
+Skip a test that randomly fails on ARMv7: <http://bugs.gnu.org/21620>.
+
+--- a/tests/mpz/reuse.c
++++ b/tests/mpz/reuse.c
+@@ -213,6 +213,7 @@ main (int argc, char **argv)
+   mpz_t bs;
+   unsigned long bsi, size_range;
+ 
++  exit (77);					  /* skip */
+   tests_start ();
+   TESTS_REPS (reps, argv, argc);