gnu: samba: Fix fcntl hint detection in configure script.

The configure script generates a C program to detect support for
lifetime hints on files.  But this program could crash, potentially
leaving a stale unreadable file behind which could cause the
patch-generated-file-shebang phase to fail.

Reported upstream <https://bugzilla.samba.org/show_bug.cgi?id=14503>.

* gnu/packages/patches/patches/samba-fix-fcntl-hint-detection.patch: New
file.
* gnu/packages/samba.scm (samba)[origin]: Add patch.
* gnu/local.mk (dist_patch_DATA): Register patch.

gnu/local.mk

@@ -1406,6 +1406,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/pango-skip-libthai-test.patch		\
   %D%/packages/patches/pciutils-hurd-configure.patch		\
   %D%/packages/patches/ppsspp-disable-upgrade-and-gold.patch		\
+  %D%/packages/patches/samba-fix-fcntl-hint-detection.patch		\
   %D%/packages/patches/sdl-pango-api_additions.patch		\
   %D%/packages/patches/sdl-pango-blit_overflow.patch		\
   %D%/packages/patches/sdl-pango-fillrect_crash.patch		\

gnu/packages/patches/samba-fix-fcntl-hint-detection.patch

@@ -0,0 +1,55 @@
+From 454ccd986b61799908a6898a55d0480911f15306 Mon Sep 17 00:00:00 2001
+From: Ralph Boehme <slow@samba.org>
+Date: Mon, 21 Sep 2020 07:48:43 +0200
+Subject: [PATCH] s3: fix fcntl waf configure check
+
+RN: Fix fcntl waf configure check
+BUG: https://bugzilla.samba.org/show_bug.cgi?id=14503
+
+Signed-off-by: Ralph Boehme <slow@samba.org>
+Reviewed-by: Volker Lendecke <vl@samba.org>
+
+Autobuild-User(master): Volker Lendecke <vl@samba.org>
+Autobuild-Date(master): Mon Sep 21 07:26:54 UTC 2020 on sn-devel-184
+---
+ source3/wscript | 10 +++++-----
+ 1 file changed, 5 insertions(+), 5 deletions(-)
+
+diff --git a/source3/wscript b/source3/wscript
+index 840ed430c0f..d3ef346eecd 100644
+--- a/source3/wscript
++++ b/source3/wscript
+@@ -1244,7 +1244,7 @@ err:
+ 
+ int main(void)
+ {
+-        uint64_t *hint, get_hint;
++        uint64_t hint, get_hint;
+         int fd;
+ 
+         fd = open(DATA, O_RDONLY | O_CREAT | O_EXCL);
+@@ -1252,8 +1252,8 @@ int main(void)
+             goto err;
+         }
+ 
+-        *hint = RWH_WRITE_LIFE_SHORT;
+-        int ret = fcntl(fd, F_SET_RW_HINT, hint);
++        hint = RWH_WRITE_LIFE_SHORT;
++        int ret = fcntl(fd, F_SET_RW_HINT, &hint);
+         if (ret == -1) {
+             goto err;
+         }
+@@ -1267,8 +1267,8 @@ int main(void)
+             goto err;
+         }
+ 
+-        *hint = RWH_WRITE_LIFE_EXTREME;
+-        ret = fcntl(fd, F_SET_FILE_RW_HINT, hint);
++        hint = RWH_WRITE_LIFE_EXTREME;
++        ret = fcntl(fd, F_SET_FILE_RW_HINT, &hint);
+         if (ret == -1) {
+             goto err;
+         }
+-- 
+2.28.0
+

gnu/packages/samba.scm

@@ -32,6 +32,7 @@
   #:use-module (guix build-system gnu)
   #:use-module (guix licenses)
   #:use-module (guix utils)
+  #:use-module (gnu packages)
   #:use-module (gnu packages acl)
   #:use-module (gnu packages admin)
   #:use-module (gnu packages autotools)
@@ -182,6 +183,7 @@ external dependencies.")
                            "samba-" version ".tar.gz"))
        (sha256
         (base32 "1lkgih0vrarf5zy6chspkwarqdylzwr63nxr3qjkpazrs86nlm9h"))
+       (patches (search-patches "samba-fix-fcntl-hint-detection.patch"))
        (modules '((guix build utils)))
        (snippet
         '(begin