package/lxc: fix build when __NR_signalfd is not available

Fixes:
 - http://autobuild.buildroot.org/results/75096a48d2dbda57459523db3ed0952e63f93535

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/lxc/0001-syscall-don-t-fail-if-__NR_signalfd-is-not-defined.patch

@@ -0,0 +1,54 @@
+From 3341e204dc1e1da6ecbc1ffbe59fca33f23ca557 Mon Sep 17 00:00:00 2001
+From: Fabrice Fontaine <fontaine.fabrice@gmail.com>
+Date: Tue, 28 Jul 2020 12:31:31 +0200
+Subject: [PATCH] syscall: don't fail if __NR_signalfd is not defined
+
+lxc fails to build if __NR_signalfd is not defined since version 4.0.0
+and
+https://github.com/lxc/lxc/commit/bed09c9cc0bec7bbd2442fcce4a2a0f03994cb09
+
+However, some architectures don't define __NR_signalfd but only
+__NR_signalfd4. This is the case for example for nios2 or csky:
+https://github.com/bminor/glibc/blob/f9ac84f92f151e07586c55e14ed628d493a5929d/sysdeps/unix/sysv/linux/nios2/arch-syscall.h
+https://github.com/bminor/glibc/blob/f9ac84f92f151e07586c55e14ed628d493a5929d/sysdeps/unix/sysv/linux/csky/arch-syscall.h
+
+Fixes:
+ - http://autobuild.buildroot.org/results/75096a48d2dbda57459523db3ed0952e63f93535
+
+Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
+[Retrieved from:
+https://github.com/lxc/lxc/commit/3341e204dc1e1da6ecbc1ffbe59fca33f23ca557]
+---
+ src/lxc/syscall_numbers.h  | 3 ---
+ src/lxc/syscall_wrappers.h | 2 ++
+ 2 files changed, 2 insertions(+), 3 deletions(-)
+
+diff --git a/src/lxc/syscall_numbers.h b/src/lxc/syscall_numbers.h
+index e2e7883786..72e4ffe460 100644
+--- a/src/lxc/syscall_numbers.h
++++ b/src/lxc/syscall_numbers.h
+@@ -228,9 +228,6 @@
+ 		#if _MIPS_SIM == _MIPS_SIM_ABI64	/* n64 */
+ 			#define __NR_signalfd 5276
+ 		#endif
+-	#else
+-		#define -1
+-		#warning "__NR_signalfd not defined for your architecture"
+ 	#endif
+ #endif
+ 
+diff --git a/src/lxc/syscall_wrappers.h b/src/lxc/syscall_wrappers.h
+index 220ef65fde..6aaa437226 100644
+--- a/src/lxc/syscall_wrappers.h
++++ b/src/lxc/syscall_wrappers.h
+@@ -112,8 +112,10 @@ static inline int signalfd(int fd, const sigset_t *mask, int flags)
+ 	int retval;
+ 
+ 	retval = syscall(__NR_signalfd4, fd, mask, _NSIG / 8, flags);
++#ifdef __NR_signalfd
+ 	if (errno == ENOSYS && flags == 0)
+ 		retval = syscall(__NR_signalfd, fd, mask, _NSIG / 8);
++#endif
+ 
+ 	return retval;
+ }