main/alpine-ipxe: fix aarch64 build

cherry-pick upstream PR fixing the issue

main/alpine-ipxe/APKBUILD

@@ -3,7 +3,7 @@
 pkgname=alpine-ipxe
 pkgver=1.0_git20180825
 _sha=133f4c47baef6002b2ccb4904a035cda2303c6e5
-pkgrel=0
+pkgrel=1
 pkgdesc="iPXE build for Alpine Linux netboot"
 url="https://boot.alpinelinux.org"
 arch="x86 x86_64 aarch64"
@@ -14,6 +14,7 @@ options="!strip !check !archcheck !tracedeps" # no tests
 install=""
 subpackages=""
 source="ipxe-$pkgver.tar.gz::https://github.com/ipxe/ipxe/archive/$_sha.tar.gz
+	fix-aarch64.patch
 	DST_Root_CA_X3.pem
 	alpine-netboot-ca.crt
 	boot.ipxe
@@ -38,6 +39,8 @@ for _target in $_targets; do
 done
 
 prepare() {
+	default_prepare
+
 	cd "$builddir"
 	local general="DIGEST_CMD NET_PROTO_IPV6 DOWNLOAD_PROTO_HTTPS IMAGE_TRUST_CMD
 		NSLOOKUP_CMD PING_CMD REBOOT_CMD NTP_CMD PCI_CMD TIME_CMD VLAN_CMD"
@@ -76,6 +79,7 @@ _split() {
 }
 
 sha512sums="fee3e1ab3951c9fed4c84a7f812341389873a919c8c38c45874d830fbaec3e40c02fa245a57cd0a251f41a8581d3f0739d9135009b1e644054faf6ef89130792  ipxe-1.0_git20180825.tar.gz
+b64be052649c62195000801b3d7762eb97f6a98a0c18f2d4bf719b35ceb07230adb71ed5452d7a6eeaf424ca3033552456a56fac99d40c18a04c94b79ad4a636  fix-aarch64.patch
 1f52b62aa9e3ec0656ea3cb5c8e52eda924d58728e64bb03ca6c112858b91b13cf0a9328b105bb232973e240406b240ed14e72b5bd325e82e6fddf3126dbcc58  DST_Root_CA_X3.pem
 68030e3f30983ee45c7f740445a246ea0df225becdd0644e06ffdbd84682ac576934dab79fecceb31b70929d81ce85b40301a977862bf7beb042270be21e6d34  alpine-netboot-ca.crt
 5a4f1edd0178e696e919e93b90689091f669bffe77ebb9da10d4872d208205fe42b285551f541a07b2067054a2344639052e2b297a582a1f71d907797a77d719  boot.ipxe"

main/alpine-ipxe/fix-aarch64.patch

+From 0d245e1f23449426503d0856bf259fa3841dae43 Mon Sep 17 00:00:00 2001
+From: "John L. Jolly" <jjolly@suse.com>
+Date: Fri, 12 Oct 2018 16:42:56 +0000
+Subject: [PATCH] [build] Fix asm argument modifiers for aarch64 build
+
+When building bin-arm64-efi/snp.efi using the gcc8 compiler, the following error occurs:
+
+    In file included from core/xferbuf.c:28:
+    core/xferbuf.c: In function 'xferbuf_malloc_realloc':
+    include/errno.h:261:2: error: invalid 'asm': invalid address mode
+      __asm__ ( ".section \".einfo\", \"\", " PROGBITS_OPS "\n\t" \
+      ^~~~~~~
+    include/errno.h:549:16: note: in expansion of macro '__einfo_error'
+     #define ENOSPC __einfo_error ( EINFO_ENOSPC )
+                    ^~~~~~~~~~~~~
+    core/xferbuf.c:192:11: note: in expansion of macro 'ENOSPC'
+       return -ENOSPC;
+               ^~~~~~
+
+The 'a' address mode is invalid for aarch64. Simply changing this to
+the constant operand type 'c' seems to resolve the issue on aarch64 and
+does not appear to affect x86_64 or i586.
+
+Signed-off-by: John L. Jolly <jjolly@suse.com>
+---
+ include/errno.h | 4 ++--
+ 1 file changed, 2 insertions(+), 2 deletions(-)
+
+diff --git a/include/errno.h b/include/errno.h
+index e80bf9ca5..342384fa4 100644
+--- a/include/errno.h
++++ b/include/errno.h
+@@ -262,10 +262,10 @@ static inline void eplatform_discard ( int dummy __unused, ... ) {}
+ 		  ".align 8\n\t"					\
+ 		  "\n1:\n\t"						\
+ 		  ".long ( 4f - 1b )\n\t"				\
+-		  ".long %a0\n\t"					\
++		  ".long %c0\n\t"					\
+ 		  ".long ( 2f - 1b )\n\t"				\
+ 		  ".long ( 3f - 1b )\n\t"				\
+-		  ".long %a1\n\t"					\
++		  ".long %c1\n\t"					\
+ 		  "\n2:\t.asciz \"" __einfo_desc ( einfo ) "\"\n\t"	\
+ 		  "\n3:\t.asciz \"" __FILE__ "\"\n\t"			\
+ 		  ".align 8\n\t"					\