temp/gcc6: add until Alpine builds it for arm

Copy Alpine's gcc6 aport to temp. They don't have it built for aarch64
and armhf at the moment. Due to dependency checks, this means we can't
build the kernels that need gcc6, even when cross compiling with
gcc6-armhf etc. See #138 for details.

temp/gcc6/204-linux_libc_has_function.patch

@@ -0,0 +1,25 @@
+From edec78452d693fb524daa9a6efd45c850b27b25c Mon Sep 17 00:00:00 2001
+From: Szabolcs Nagy <nsz@port70.net>
+Date: Fri, 6 Nov 2015 23:59:20 +0000
+Subject: [PATCH 4/6] linux_libc_has_function
+
+---
+ gcc/config/linux.c | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/gcc/config/linux.c b/gcc/config/linux.c
+index 250296b..16c3768 100644
+--- a/gcc/config/linux.c
++++ b/gcc/config/linux.c
+@@ -26,7 +26,7 @@ along with GCC; see the file COPYING3.  If not see
+ bool
+ linux_libc_has_function (enum function_class fn_class)
+ {
+-  if (OPTION_GLIBC)
++  if (OPTION_GLIBC || OPTION_MUSL)
+     return true;
+   if (OPTION_BIONIC)
+     if (fn_class == function_c94
+-- 
+2.8.1
+