package/xen: fix build with gcc 11

Fix the following build failure with gcc 11:

linux.c:165:50: error: argument 7 of type 'const xen_pfn_t[]' {aka 'const long long unsigned int[]'} declared as an ordinary array [-Werror=vla-parameter]
  165 |                                  const xen_pfn_t arr[/*num*/], int err[/*num*/])
      |                                  ~~~~~~~~~~~~~~~~^~~~~~~~~~~~
In file included from linux.c:29:
private.h:35:50: note: previously declared as a variable length array 'const xen_pfn_t[num]' {aka 'const long long unsigned int[num]'}
   35 |                                  const xen_pfn_t arr[num], int err[num]);
      |                                  ~~~~~~~~~~~~~~~~^~~~~~~~

Fixes:
 - http://autobuild.buildroot.org/results/f70d060cf50254694113f19f50a8ef96ef33dd1a

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

package/xen/0002-libs-foreignmemory-Fix-osdep_xenforeignmemory_map-prototype.patch

@@ -0,0 +1,33 @@
+From 5d3e4ebb5c71477d74a0c503438545a0126d3863 Mon Sep 17 00:00:00 2001
+From: Anthony PERARD <anthony.perard@citrix.com>
+Date: Tue, 1 Jun 2021 16:41:47 +0100
+Subject: [PATCH] libs/foreignmemory: Fix osdep_xenforeignmemory_map prototype
+
+Commit cf8c4d3d13b8 made some preparation to have one day
+variable-length-array argument, but didn't declare the array in the
+function prototype the same way as in the function definition. And now
+GCC 11 complains about it.
+
+Fixes: cf8c4d3d13b8 ("tools/libs/foreignmemory: pull array length argument to map forward")
+Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
+Reviewed-by: Jan Beulich <jbeulich@suse.com>
+[Retrieved from:
+https://github.com/xen-project/xen/commit/5d3e4ebb5c71477d74a0c503438545a0126d3863]
+Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
+---
+ tools/libs/foreignmemory/private.h | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/tools/libs/foreignmemory/private.h b/tools/libs/foreignmemory/private.h
+index 1ee3626dd278..5bb0cefb0987 100644
+--- a/tools/libs/foreignmemory/private.h
++++ b/tools/libs/foreignmemory/private.h
+@@ -32,7 +32,7 @@ int osdep_xenforeignmemory_close(xenforeignmemory_handle *fmem);
+ void *osdep_xenforeignmemory_map(xenforeignmemory_handle *fmem,
+                                  uint32_t dom, void *addr,
+                                  int prot, int flags, size_t num,
+-                                 const xen_pfn_t arr[num], int err[num]);
++                                 const xen_pfn_t arr[/*num*/], int err[/*num*/]);
+ int osdep_xenforeignmemory_unmap(xenforeignmemory_handle *fmem,
+                                  void *addr, size_t num);
+