gnu: sharutils: Fix bundled gnulib.

* gnu/packages/compression.scm (sharutils)[source]: Add snippet to fix
bundled gnulib.

gnu/packages/compression.scm

@@ -584,7 +584,23 @@ decompressors when faced with corrupted input.")
       (patches (search-patches "sharutils-CVE-2018-1000097.patch"))
       (sha256
        (base32
-        "16isapn8f39lnffc3dp4dan05b7x6mnc76v6q5nn8ysxvvvwy19b"))))
+        "16isapn8f39lnffc3dp4dan05b7x6mnc76v6q5nn8ysxvvvwy19b"))
+             (modules '((guix build utils)))
+             (snippet
+              '(begin
+                 ;; Adjust the bundled gnulib to work with glibc 2.28.  See e.g.
+                 ;; "m4-gnulib-libio.patch".  This is a phase rather than patch
+                 ;; or snippet to work around <https://bugs.gnu.org/32347>.
+                 (substitute* (find-files "lib" "\\.c$")
+                   (("#if defined _IO_ftrylockfile")
+                    "#if defined _IO_EOF_SEEN"))
+                 (substitute* "lib/stdio-impl.h"
+                   (("^/\\* BSD stdio derived implementations")
+                    (string-append "#if !defined _IO_IN_BACKUP && defined _IO_EOF_SEEN\n"
+                                   "# define _IO_IN_BACKUP 0x100\n"
+                                   "#endif\n\n"
+                                   "/* BSD stdio derived implementations")))
+                 #t))))
     (build-system gnu-build-system)
     (inputs
      `(("which" ,which)))