Fix runtime crashes on i386: enforce stack-alignment=16

PR:		205958
Submitted by:	dim (patch via ports mailing list)
Reported by:	otacilio.neto@bsd.com.br
MFH:		2016Q4 (ports-secteam fix blanket)

multimedia/ffmpeg/Makefile

@@ -3,7 +3,7 @@
 
 PORTNAME=	ffmpeg
 PORTVERSION=	2.8.8
-PORTREVISION=	3
+PORTREVISION=	4
 PORTEPOCH=	1
 CATEGORIES=	multimedia audio ipv6 net
 MASTER_SITES=	http://ffmpeg.org/releases/

multimedia/ffmpeg/files/patch-configure

@@ -14,6 +14,19 @@
  cpu="generic"
  intrinsics="none"
  
+@@ -5682,7 +5677,11 @@ elif enabled gcc; then
+ elif enabled llvm_gcc; then
+     check_cflags -mllvm -stack-alignment=16
+ elif enabled clang; then
+-    check_cflags -mllvm -stack-alignment=16
++    if enabled x86_32; then
++        check_cflags -mllvm -stack-alignment=16
++        check_cflags -mstack-alignment=16
++        check_cflags -mstackrealign
++    fi
+     check_cflags -Qunused-arguments
+     check_cflags -Werror=implicit-function-declaration
+     check_cflags -Werror=missing-prototypes
 @@ -5823,7 +5818,7 @@ ifndef MAIN_MAKEFILE
  SRC_PATH:=\$(SRC_PATH:.%=..%)
  endif