gnu: sed, diffutils: Patch faulty Gnulib tests.

This is a followup to c823b95825, fixing
tests for sed and diffutils on armhf-linux.

* gnu/packages/base.scm (sed)[source]: Add
"coreutils-gnulib-tests.patch".
(diffutils)[source]: Likewise.
* gnu/packages/commencement.scm (diffutils-boot0)[source]: New field.

gnu/packages/base.scm

@@ -148,6 +148,8 @@ including, for example, recursive directory searching.")
             (sha256
              (base32
               "0alqagh0nliymz23kfjg6g9w3cr086k0sfni56gi8fhzqwa3xksk"))
+            (patches (search-patches "coreutils-gnulib-tests.patch"))
+
             ;; Remove this snippet once upstream releases a fixed version.
             ;; This snippet changes Makefile.in, even though the upstream
             ;; patch changes testsuite/local.mk, since we build sed from a
@@ -269,7 +271,8 @@ differences.")
                                 version ".tar.xz"))
             (sha256
              (base32
-              "09isrg0isjinv8c535nxsi1s86wfdfzml80dbw41dj9x3hiad9xk"))))
+              "09isrg0isjinv8c535nxsi1s86wfdfzml80dbw41dj9x3hiad9xk"))
+            (patches (search-patches "coreutils-gnulib-tests.patch"))))
    (build-system gnu-build-system)
    (native-inputs (list perl))
    (synopsis "Comparing and merging files")

gnu/packages/commencement.scm

@@ -2474,6 +2474,9 @@ exec " gcc "/bin/" program
   (package
     (inherit diffutils)
     (name "diffutils-boot0")
+    (source (origin
+              (inherit (package-source diffutils))
+              (patches '())))                 ;patches for tests unneeded here
     (native-inputs `())
     (inputs
      `(("make" ,gnu-make-boot0)