package/libnss: fix PowerPC build failure

NSS assumes <sys/auvx.h> is always present but that's not true, so add a
patch to check if it exists or not.

Fixes:

  http://autobuild.buildroot.net/results/425ba828d30c2bd55ce9f4f00e67bc10d9de2867/

Signed-off-by: Giulio Benetti <giulio.benetti@benettiengineering.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/libnss/0001-Bug-1614183-Check-if-PPC-__has_include-sys-auxv.h.patch

@@ -0,0 +1,51 @@
+From d9c7cbb3660d8a2da9ce42e4d1b58642a256a91a Mon Sep 17 00:00:00 2001
+From: Giulio Benetti <giulio.benetti@benettiengineering.com>
+Date: Sun, 9 Feb 2020 10:15:16 +0100
+Subject: [PATCH] Bug 1614183 - Check if PPC __has_include(<sys/auxv.h>)
+
+Some build environment doesn't provide <sys/auxv.h> and this causes
+build failure, so let's check if that header exists by using
+__has_include() helper.
+
+Signed-off-by: Giulio Benetti <giulio.benetti@benettiengineering.com>
+---
+ nss/lib/freebl/blinit.c | 10 ++++++++++
+ 1 file changed, 10 insertions(+)
+
+diff --git a/nss/lib/freebl/blinit.c b/nss/lib/freebl/blinit.c
+index 7e8adfc64..d4921aaee 100644
+--- a/nss/lib/freebl/blinit.c
++++ b/nss/lib/freebl/blinit.c
+@@ -431,8 +431,14 @@ ppc_crypto_support()
+ 
+ #if defined(__powerpc__)
+ 
++#ifndef __has_include
++#define __has_include(x) 0
++#endif
++
+ #if defined(__linux__) || (defined(__FreeBSD__) && __FreeBSD__ >= 12)
++#if __has_include(<sys/auxv.h>)
+ #include <sys/auxv.h>
++#endif
+ #elif (defined(__FreeBSD__) && __FreeBSD__ < 12)
+ #include <sys/sysctl.h>
+ #endif
+@@ -449,10 +455,14 @@ CheckPPCSupport()
+ 
+     unsigned long hwcaps = 0;
+ #if defined(__linux__)
++#if __has_include(<sys/auxv.h>)
+     hwcaps = getauxval(AT_HWCAP2);
++#endif
+ #elif defined(__FreeBSD__)
+ #if __FreeBSD__ >= 12
++#if __has_include(<sys/auxv.h>)
+     elf_aux_info(AT_HWCAP2, &hwcaps, sizeof(hwcaps));
++#endif
+ #else
+     size_t len = sizeof(hwcaps);
+     sysctlbyname("hw.cpu_features2", &hwcaps, &len, NULL, 0);
+-- 
+2.20.1
+