Don't use linux.h for non-Linux targets

[Joseph S. Myers]

On Wed, 27 Apr 2011, Thomas Schwinge wrote:

> One (minor) additional idea: for clarity, shouldn't it now be possible to
> remove any #undef GNU_USER_TARGET_OS_CPP_BUILTINS, #undef
> GNU_USER_DYNAMIC_LINKER, #undef GNU_USER_LINK_EMULATION, etc. from
> *gnu.h?  I don't expect you to test this; I'll have a look later on.

Yes, if those were only to undefine macros defined in linux.h.  In general 
there is no consistent rule about whether headers use #undef in cases 
where it is not needed.

-- 
Joseph S. Myers
joseph@codesourcery.com