gcc: fix build of libsanitizer in gcc 4.9 and 5.x on PowerPC

libsanitizer in gcc fails to build on PowerPC with gcc versions 4.9
and 5.x used in conjunction with glibc 2.25, with the following error:

../../../../gcc-host/libsanitizer/asan/asan_linux.cc: In function 'bool __asan::AsanInterceptsSignal(int)':
../../../../gcc-host/libsanitizer/asan/asan_linux.cc:222:20: error: 'SIGSEGV' was not declared in this scope
   return signum == SIGSEGV && common_flags()->handle_segv;

This commit adds a patch that has been submitted to upstream gcc
(https://patchwork.ozlabs.org/patch/725596/) but not merged. The patch
is no longer needed with gcc 6.x and later because the code has been
reworked.

Fixes Buildroot bug #10061

Signed-off-by: Matthew Weber <matthew.weber@rockwellcollins.com>
[Thomas: rework commit log.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

(cherry picked from commit 5c90f6a7b68ebdc43ea72b763ec98a0a300c57a1)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/gcc/4.9.4/942-asan-fix-missing-include-signal-h.patch

@@ -0,0 +1,36 @@
+From 205aa8e97bab553e5e6fe45896325e97962de704 Mon Sep 17 00:00:00 2001
+From: Rolf Eike Beer <eb@emlix.com>
+Date: Wed, 8 Feb 2017 11:42:52 +0100
+Subject: [PATCH] asan: fix missing include of signal.h
+
+This breaks when building gcc 4.9.4 / 5.4.0 with
+target_platform=powerpc-unknown-linux-gnu with glibc 2.25:
+
+../../../../gcc-host/libsanitizer/asan/asan_linux.cc: In function 'bool __asan::AsanInterceptsSignal(int)':
+../../../../gcc-host/libsanitizer/asan/asan_linux.cc:222:20: error: 'SIGSEGV' was not declared in this scope
+   return signum == SIGSEGV && common_flags()->handle_segv;
+
+This has been verified to apply to at least 4.9.4 and up to 5.4,
+the code has been reworked for gcc 6.
+
+Resolves (Buildroot) Bug: https://bugs.busybox.net/show_bug.cgi?id=10061
+
+Upstream: https://patchwork.ozlabs.org/patch/725596/
+
+Signed-off-by: Matthew Weber <matthew.weber@rockwellcollins.com>
+---
+ libsanitizer/asan/asan_linux.cc | 1 +
+ 1 file changed, 1 insertion(+)
+
+diff --git a/libsanitizer/asan/asan_linux.cc b/libsanitizer/asan/asan_linux.cc
+index c504168..59087b9 100644
+--- a/libsanitizer/asan/asan_linux.cc
++++ b/libsanitizer/asan/asan_linux.cc
+@@ -29,6 +29,7 @@
+ #include <dlfcn.h>
+ #include <fcntl.h>
+ #include <pthread.h>
++#include <signal.h>
+ #include <stdio.h>
+ #include <unistd.h>
+ #include <unwind.h>

package/gcc/5.4.0/942-asan-fix-missing-include-signal-h.patch

@@ -0,0 +1,36 @@
+From 205aa8e97bab553e5e6fe45896325e97962de704 Mon Sep 17 00:00:00 2001
+From: Rolf Eike Beer <eb@emlix.com>
+Date: Wed, 8 Feb 2017 11:42:52 +0100
+Subject: [PATCH] asan: fix missing include of signal.h
+
+This breaks when building gcc 4.9.4 / 5.4.0 with
+target_platform=powerpc-unknown-linux-gnu with glibc 2.25:
+
+../../../../gcc-host/libsanitizer/asan/asan_linux.cc: In function 'bool __asan::AsanInterceptsSignal(int)':
+../../../../gcc-host/libsanitizer/asan/asan_linux.cc:222:20: error: 'SIGSEGV' was not declared in this scope
+   return signum == SIGSEGV && common_flags()->handle_segv;
+
+This has been verified to apply to at least 4.9.4 and up to 5.4,
+the code has been reworked for gcc 6.
+
+Resolves (Buildroot) Bug: https://bugs.busybox.net/show_bug.cgi?id=10061
+
+Upstream: https://patchwork.ozlabs.org/patch/725596/
+
+Signed-off-by: Matthew Weber <matthew.weber@rockwellcollins.com>
+---
+ libsanitizer/asan/asan_linux.cc | 1 +
+ 1 file changed, 1 insertion(+)
+
+diff --git a/libsanitizer/asan/asan_linux.cc b/libsanitizer/asan/asan_linux.cc
+index c504168..59087b9 100644
+--- a/libsanitizer/asan/asan_linux.cc
++++ b/libsanitizer/asan/asan_linux.cc
+@@ -29,6 +29,7 @@
+ #include <dlfcn.h>
+ #include <fcntl.h>
+ #include <pthread.h>
++#include <signal.h>
+ #include <stdio.h>
+ #include <unistd.h>
+ #include <unwind.h>