[MinGW] Set NATIVE_SYSTEM_HEADER_DIR relative to configured prefix

[Daniel Jacobowitz]

On Mon, Dec 18, 2006 at 12:47:40PM -0800, Brian Dessent wrote:
> Putting aside the idea of a relocatable compiler for a moment, you
> appear to be confused about DESTDIR.  This is meant to be used to
> install files to a *temporary* staging location.  You should never try
> to run them from there.  They will only work when they are located in
> the place specified by prefix.
> 
> Now, in the specific case of the MinGW target, there is supposed to be
> code in the driver that locates everything relative to the binaries
> rather than using the configured absolute paths, so that the above
> restriction is lifted.  But it would seem that either this code has
> bitrotted or something else is wrong.

In fact the compiler is supposed to be relocatable on _all_ platforms,
so should work when run from DESTDIR.  Some things are searched for in
a relocated location, others in an unrelocated location, depending on
the platform.

-- 
Daniel Jacobowitz
CodeSourcery