build: fix linker flags for executable on MacOS

This patch fixes inaccuracy in Tarantool build configuration introduced
by commit 07c83aab ('build: adjust
LuaJIT build system'). All those MacOS-related tweaks for __PAGEZERO
size and preferred load address for the bundle are necessary only for
builds with 32-bit GC area on 64-bit host. The only case fitting these
conditions is x86_64 with no LUAJIT_ENABLE_GC64. All other 64-bit builds
use 64-bit GC area unconditionally.

Part of #5983
Needed for #5629
Follows up #4862

Reviewed-by: Sergey Kaplun <skaplun@tarantool.org>
Reviewed-by: Nikita Pettik <korablev@tarantool.org>
Reviewed-by: Sergey Ostanevich <sergos@tarantool.org>
Signed-off-by: Igor Munkin <imun@tarantool.org>