pkg/51122: with gcc 5.x x86 32-bit ffmpeg2 and ffmpeg3 need extra compile flags

[Onno van der Linden <o.vd.linden%quicknet.nl@localhost>]

>Number:         51122
>Category:       pkg
>Synopsis:       ffmpeg[23] compiled with gcc 5.x on x86 32-bit can lead to crashes
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    pkg-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat May 07 18:50:00 +0000 2016
>Originator:     Onno van der Linden
>Release:        NetBSD 7.99.29
>Organization:
	<organization of PR author (multiple lines)>
>Environment:
System: NetBSD sheep 7.99.29 NetBSD 7.99.29 (SHEEP) #0: Sun May 1 19:11:17 MEST 2016 onno@sheep:/usr/src/sys/arch/i386/compile/SHEEP i386
Architecture: i386
Machine: i386
>Description:
	gcc 5.x on x86 32-bit needs -mstackrealign -mpreferred-stack-boundary=4
        see pkg/48860.
>How-To-Repeat:
	x86 32-bit firefox linked against ffmpeg3 compiled with gcc 5.x crashes
while browsing twitter.com. Stack trace shows an sse2 function from libavcodec
>Fix:
--- ffmpeg2/Makefile.orig	2016-05-07 16:47:52.713391361 +0200
+++ ffmpeg2/Makefile	2016-05-07 16:47:57.249262990 +0200
@@ -49,7 +49,7 @@
    || !empty(CC_VERSION:Mgcc-4.[01].*) \
    || empty(CC_VERSION:Mgcc*)
 CONFIGURE_ARGS+=	--disable-asm
-.  elif !empty(CC_VERSION:Mgcc-4.*)
+.  else
 CFLAGS+=		-mstackrealign -mpreferred-stack-boundary=4
 .  endif
 .endif
--- ffmpeg3/Makefile.orig	2016-05-07 16:47:05.028467467 +0200
+++ ffmpeg3/Makefile	2016-05-07 16:47:11.431340768 +0200
@@ -49,7 +49,7 @@
    || !empty(CC_VERSION:Mgcc-4.[01].*) \
    || empty(CC_VERSION:Mgcc*)
 CONFIGURE_ARGS+=	--disable-asm
-.  elif !empty(CC_VERSION:Mgcc-4.*)
+.  else
 CFLAGS+=		-mstackrealign -mpreferred-stack-boundary=4
 .  endif
 .endif