Disable LuaJIT on non-x86 architectures

The version of LuaJIT in port doesn't work well (or at all) for neovim
on non-x86 architectures. Plus, some users (at least the submitter, who
made a good argument for it) may not want LuaJIT at all.

So, make LuaJIT an OPTION. Enable it by default, and exclude it from
all the archs that LuaJIT+neovim doesn't work on. Fall back instead on
normal Lua.

PR:		238079
Submitted by:	Greg V
MFH:		2019Q2

editors/neovim/Makefile

@@ -4,6 +4,7 @@
 PORTNAME=	neovim
 DISTVERSIONPREFIX=	v
 DISTVERSION=	0.3.5
+PORTREVISION=	1
 CATEGORIES=	editors
 
 MAINTAINER=	adamw@FreeBSD.org
@@ -14,8 +15,7 @@ LICENSE=	APACHE20
 BUILD_DEPENDS=	gperf:devel/gperf \
 		${LUA_MODLIBDIR}/bit.so:devel/lua-bitop \
 		${LUA_MODLIBDIR}/lpeg.so:devel/lua-lpeg
-LIB_DEPENDS=	libluajit-5.1.so:lang/luajit \
-		libmsgpackc.so:devel/msgpack \
+LIB_DEPENDS=	libmsgpackc.so:devel/msgpack \
 		libtermkey.so:devel/libtermkey \
 		libunibilium.so:devel/unibilium \
 		libuv.so:devel/libuv \
@@ -25,7 +25,7 @@ TEST_DEPENDS=	autoconf>=0:devel/autoconf \
 		gmake:devel/gmake \
 		libtool:devel/libtool
 
-USES=		cmake iconv lua:build pathfix pkgconfig
+USES=		cmake iconv pathfix pkgconfig
 USE_GITHUB=	yes
 GH_TUPLE=	libmpack:libmpack:1.0.5:libmpack \
 		libmpack:libmpack-lua:1.0.7:libmpack_lua
@@ -34,8 +34,20 @@ CMAKE_ARGS=	-DLUA_PRG:FILEPATH="${LUA_CMD}" \
 		-DCMAKE_INSTALL_MANDIR:PATH="${MANPREFIX}/man" \
 		-DDEPS_PREFIX:PATH="${LOCALBASE}"
 
-OPTIONS_DEFINE=	NLS PYNVIM
+OPTIONS_DEFINE=	LUAJIT NLS PYNVIM
+OPTIONS_DEFAULT=LUAJIT
+OPTIONS_EXCLUDE_aarch64=LUAJIT
+OPTIONS_EXCLUDE_mips64=	LUAJIT
+OPTIONS_EXCLUDE_powerpc64=	LUAJIT
+OPTIONS_EXCLUDE_riscv=	LUAJIT
+OPTIONS_EXCLUDE_sparc64=LUAJIT
 OPTIONS_SUB=	yes
+
+LUAJIT_DESC=	Use LuaJIT for faster Lua code
+LUAJIT_LIB_DEPENDS=	libluajit-5.1.so:lang/luajit
+LUAJIT_USES=		lua:build
+LUAJIT_CMAKE_OFF=	-DPREFER_LUA:BOOL="ON"
+LUAJIT_USES_OFF=	lua:52
 NLS_CMAKE_BOOL=	ENABLE_LIBINTL
 NLS_USES=	gettext
 PYNVIM_DESC=	Enable support for plugins written in python