Add a MULTILIB option to gcc{,48,49,5} for powerpc64

This change is the same as r400632, which updated gcc[56]-devel, but now
for gcc{,48,49,5}.  Waited a week to ensure the change caused nothing to go
horribly wrong but this change is very low risk because it only affects
powerpc64.

This fixes the build of gcc{,48,49,5} under powerpc64 when the system
is built without the lib32 libraries.

More in detail:

If the system is built with lib32 support (WITH_LIB32, which is the default),
building gcc from ports results in a compiler that can target both 64-bit and
32-bit binaries on powerpc64.  However, when lib32 support is disabled
(WITHOUT_LIB32), gcc should only be built with 64-bit support or otherwise
the build fails.

To fix this, explicitly disable 32-bit support when /usr/lib32 is not present
and add a MULTILIB option (which is only defined for powerpc64 when 32-bit
support is possible and defaults to yes to preserve the current behavior) to
allow the user to explicitly control this feature.

Approved by:    gerald (maintainer), bdrewery (mentor), andreast
Differential Revision:  https://reviews.freebsd.org/D3952

lang/gcc/Makefile

@@ -3,6 +3,7 @@
 
 PORTNAME=	gcc
 PORTVERSION=	4.8.5
+PORTREVISION=	1
 CATEGORIES=	lang java
 MASTER_SITES=	GCC/releases/gcc-${DISTVERSION}
 
@@ -46,6 +47,14 @@ OPTIONS_DEFAULT_i386=	JAVA
 OPTIONS_DEFAULT_amd64=	JAVA
 OPTIONS_EXCLUDE_DragonFly=	JAVA
 BOOTSTRAP_DESC=		Build using a full bootstrap
+.if exists(/usr/lib32/libc.so)
+OPTIONS_DEFINE+=	MULTILIB
+OPTIONS_DEFAULT+=	MULTILIB
+MULTILIB_DESC=		Build support for 32-bit and 64-bit target types
+MULTILIB_CONFIGURE_ENABLE=	multilib
+.else
+CONFIGURE_ARGS+=	--disable-multilib
+.endif
 
 .include <bsd.port.pre.mk>
 

lang/gcc48/Makefile

@@ -3,6 +3,7 @@
 
 PORTNAME=	gcc
 PORTVERSION=	4.8.5
+PORTREVISION=	1
 CATEGORIES=	lang java
 MASTER_SITES=	GCC/releases/gcc-${DISTVERSION}
 PKGNAMESUFFIX=	${SUFFIX}
@@ -49,6 +50,14 @@ OPTIONS_DEFAULT_i386=	JAVA
 OPTIONS_DEFAULT_amd64=	JAVA
 OPTIONS_EXCLUDE_DragonFly=	JAVA
 BOOTSTRAP_DESC=		Build using a full bootstrap
+.if exists(/usr/lib32/libc.so)
+OPTIONS_DEFINE+=	MULTILIB
+OPTIONS_DEFAULT+=	MULTILIB
+MULTILIB_DESC=		Build support for 32-bit and 64-bit target types
+MULTILIB_CONFIGURE_ENABLE=	multilib
+.else
+CONFIGURE_ARGS+=	--disable-multilib
+.endif
 
 .include <bsd.port.pre.mk>
 

lang/gcc49/Makefile

@@ -3,6 +3,7 @@
 
 PORTNAME=	gcc
 PORTVERSION=	4.9.4.s20151028
+PORTREVISION=	1
 CATEGORIES=	lang java
 MASTER_SITES=	GCC/snapshots/${DISTVERSION}
 PKGNAMESUFFIX=	${SUFFIX}
@@ -50,6 +51,14 @@ OPTIONS_DEFAULT_i386=	JAVA
 OPTIONS_DEFAULT_amd64=	JAVA
 OPTIONS_EXCLUDE_DragonFly=	JAVA
 BOOTSTRAP_DESC=		Build using a full bootstrap
+.if exists(/usr/lib32/libc.so)
+OPTIONS_DEFINE+=	MULTILIB
+OPTIONS_DEFAULT+=	MULTILIB
+MULTILIB_DESC=		Build support for 32-bit and 64-bit target types
+MULTILIB_CONFIGURE_ENABLE=	multilib
+.else
+CONFIGURE_ARGS+=	--disable-multilib
+.endif
 
 .include <bsd.port.pre.mk>
 

lang/gcc5/Makefile

@@ -3,7 +3,7 @@
 
 PORTNAME=	gcc
 PORTVERSION=	5.2.0
-PORTREVISION=	1
+PORTREVISION=	2
 CATEGORIES=	lang java
 MASTER_SITES=	GCC/releases/gcc-${DISTVERSION}
 PKGNAMESUFFIX=	${SUFFIX}
@@ -52,6 +52,15 @@ OPTIONS_DEFAULT_amd64=	JAVA
 OPTIONS_EXCLUDE_DragonFly=	JAVA
 BOOTSTRAP_DESC=		Build using a full bootstrap
 
+.if exists(/usr/lib32/libc.so)
+OPTIONS_DEFINE_powerpc64=	MULTILIB
+OPTIONS_DEFAULT_powerpc64=	MULTILIB
+MULTILIB_DESC=		Build support for 32-bit and 64-bit targets
+MULTILIB_CONFIGURE_ENABLE=	multilib
+.else
+CONFIGURE_ARGS+=	--disable-multilib
+.endif
+
 .include <bsd.port.pre.mk>
 
 .if ${ARCH} == "amd64"