package/xen: fix build with gcc 8.1

Fixes:
 - http://autobuild.buildroot.org/results/df5abe6ca8b4c8935f3d5c257aef816190771200

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
(cherry picked from commit 9b2bf1b7458891ae652e3493ae87d1f7c4776a8b)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/xen/0004-xenpmd-make-32-bit-gcc-8-1-non-debug-build-work.patch

@@ -0,0 +1,79 @@
+From e75c9dc85fdeeeda0b98d8cd8d784e0508c3ffb8 Mon Sep 17 00:00:00 2001
+From: Wei Liu <wei.liu2@citrix.com>
+Date: Thu, 26 Jul 2018 15:58:54 +0100
+Subject: [PATCH] xenpmd: make 32 bit gcc 8.1 non-debug build work
+
+32 bit gcc 8.1 non-debug build yields:
+
+xenpmd.c:354:23: error: '%02x' directive output may be truncated writing between 2 and 8 bytes into a region of size 3 [-Werror=format-truncation=]
+     snprintf(val, 3, "%02x",
+                       ^~~~
+xenpmd.c:354:22: note: directive argument in the range [40, 2147483778]
+     snprintf(val, 3, "%02x",
+                      ^~~~~~
+xenpmd.c:354:5: note: 'snprintf' output between 3 and 9 bytes into a destination of size 3
+     snprintf(val, 3, "%02x",
+     ^~~~~~~~~~~~~~~~~~~~~~~~
+              (unsigned int)(9*4 +
+              ~~~~~~~~~~~~~~~~~~~~
+                             strlen(info->model_number) +
+                             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+                             strlen(info->serial_number) +
+                             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+                             strlen(info->battery_type) +
+                             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+                             strlen(info->oem_info) + 4));
+                             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+All info->* used in calculation are 32 bytes long, and the parsing
+code makes sure they are null-terminated, so the end result of the
+expression won't exceed 255, which should be able to be fit into 3
+bytes in hexadecimal format.
+
+Add an assertion to make gcc happy.
+
+Signed-off-by: Wei Liu <wei.liu2@citrix.com>
+Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
+Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
+[Retrieved from:
+https://github.com/xen-project/xen/commit/e75c9dc85fdeeeda0b98d8cd8d784e0508c3ffb8]
+---
+ tools/xenpmd/xenpmd.c | 12 ++++++------
+ 1 file changed, 6 insertions(+), 6 deletions(-)
+
+diff --git a/tools/xenpmd/xenpmd.c b/tools/xenpmd/xenpmd.c
+index 56412a9a81c..1c801caa712 100644
+--- a/tools/xenpmd/xenpmd.c
++++ b/tools/xenpmd/xenpmd.c
+@@ -40,6 +40,7 @@
+ #include <unistd.h>
+ #include <sys/stat.h>
+ #include <xenstore.h>
++#include <assert.h>
+ 
+ /* #define RUN_STANDALONE */
+ #define RUN_IN_SIMULATE_MODE
+@@ -345,18 +346,17 @@ void write_ulong_lsb_first(char *temp_val, unsigned long val)
+ void write_battery_info_to_xenstore(struct battery_info *info)
+ {
+     char val[1024], string_info[256];
++    unsigned int len;
+ 
+     xs_mkdir(xs, XBT_NULL, "/pm");
+    
+     memset(val, 0, 1024);
+     memset(string_info, 0, 256);
+     /* write 9 dwords (so 9*4) + length of 4 strings + 4 null terminators */
+-    snprintf(val, 3, "%02x", 
+-             (unsigned int)(9*4 +
+-                            strlen(info->model_number) +
+-                            strlen(info->serial_number) +
+-                            strlen(info->battery_type) +
+-                            strlen(info->oem_info) + 4));
++    len = 9 * 4 + strlen(info->model_number) + strlen(info->serial_number) +
++          strlen(info->battery_type) + strlen(info->oem_info) + 4;
++    assert(len < 255);
++    snprintf(val, 3, "%02x", len);
+     write_ulong_lsb_first(val+2, info->present);
+     write_ulong_lsb_first(val+10, info->design_capacity);
+     write_ulong_lsb_first(val+18, info->last_full_capacity);