Support installing headers for bootstrapping libgcc

[Jeff Law]

On 05/11/2012 12:54 PM, Nix wrote:
> On 11 May 2012, Roland McGrath stated:
>> I think we can just get rid of sln entirely at this point.  We really
>> don't expect anybody to be able to run 'make install' directly on a
>> live system and not ruin all sorts of things that might be needed
>> somewhere in the process.  So why should ln be different?
>
> You might well break various glibc postinstall scripts if you do that.
> (You'll certainly break mine, though I don't like sln(1) either.)
Well, sln is also quite helpful in repairing a broken system :-)
jeff