[Buildroot] external toolchain and sysroot

[Yury Luneff]

> In the busybox .mk file, I found that TARGET_LDFLAGS wasn't being used
> (it wasn't being passed to the "make" command).  I had to patch the
> .mk file to pass the TARGET_LDFLAGS value to make.

>> It is definetely not the problem of package as openvpn doesn't find 
>> openssl too and the corresponding .so files are in staging. Or it is 
>> a bug in both uemacs and openvpn which is unprobable.

as for uemacs, its link command disregarded even CFLAGS, so I had to 
patch the makefile of uemacs. So I did the uemacs (just for fun, 
really, it's old like heaven and hell :-). Same problem, I guess. 
Shouldn't it be fixed project-wide? Documentations says that CT-NG is 
ok, but reality says something different.

As for openvpn, I guess the precise commands are common for autotools 
packages, so it is not quite so easy to find the right place to 
strike.

> It sounds like the .mk files are missing something.  See the following
> bugs for patches that show how I fixed missing --sysroot problems for
> busybox and mtd-utils:

Busybox is ok :(