gnu: libmemcached: Fix build.

* gnu/packages/databases.scm (libmemcached)[source]: Add patch.
* gnu/packages/patches/libmemcached-build-with-gcc7.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add it.

gnu/local.mk

@@ -1165,6 +1165,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/mcrypt-CVE-2012-4409.patch			\
   %D%/packages/patches/mcrypt-CVE-2012-4426.patch			\
   %D%/packages/patches/mcrypt-CVE-2012-4527.patch			\
+  %D%/packages/patches/libmemcached-build-with-gcc7.patch	\
   %D%/packages/patches/mes-remove-store-name.patch		\
   %D%/packages/patches/mesa-skip-disk-cache-test.patch		\
   %D%/packages/patches/mescc-tools-boot.patch			\

gnu/packages/databases.scm

@@ -370,7 +370,9 @@ applications.")
               (file-name (string-append name "-" version "-checkout"))
               (sha256
                (base32
-                "1842s4dxdh21gdr46q4dgxigidcs6dkqnbnqjwb9l8r0bqx5nb10"))))
+                "1842s4dxdh21gdr46q4dgxigidcs6dkqnbnqjwb9l8r0bqx5nb10"))
+              (patches
+               (search-patches "libmemcached-build-with-gcc7.patch"))))
     (build-system gnu-build-system)
     (native-inputs
      `(("memcached" ,memcached)

gnu/packages/patches/libmemcached-build-with-gcc7.patch

@@ -0,0 +1,28 @@
+Author: Tobias Geerinckx-Rice <me@tobias.gr>
+Date: Wed 22 Jan 22:58:13 CET 2020
+Subject: gnu: memcached: Fix build with GCC 7.
+
+Taken verbating from this bug report:
+<https://bugs.launchpad.net/libmemcached/+bug/1663985>.
+
+diff -up ./clients/memflush.cc.old ./clients/memflush.cc
+--- ./clients/memflush.cc.old	2017-02-12 10:12:59.615209225 +0100
++++ ./clients/memflush.cc	2017-02-12 10:13:39.998382783 +0100
+@@ -39,7 +39,7 @@ int main(int argc, char *argv[])
+ {
+   options_parse(argc, argv);
+ 
+-  if (opt_servers == false)
++  if (!opt_servers)
+   {
+     char *temp;
+ 
+@@ -48,7 +48,7 @@ int main(int argc, char *argv[])
+       opt_servers= strdup(temp);
+     }
+ 
+-    if (opt_servers == false)
++    if (!opt_servers)
+     {
+       std::cerr << "No Servers provided" << std::endl;
+       exit(EXIT_FAILURE);