[PATCH] Fix in-srcdir build of gcc

[Paolo Bonzini]

> As I am a proponent of "principle of least surprise"

I am too.  Unfortunately this patch on one hand makes ./configure work 
for gcc, on the other hand it makes it more "surprising" for 
binutils/gdb.  I am especially concerned about gdb, because of the two 
it is the one that is most likely to be built by casual users doing 
"./configure && make".

In-srcdir toplevel bootstrap definitely won't work without a patch such 
as this, because it wants to symlink or rename directories (e.g. 
stage2-gcc is linked to gcc, and stage1-gcc is linked to prev-gcc).  But 
maybe for the non-bootstrap case (and for gcc), it is enough on systems 
that support symlinks to symlink the current directory to the host 
directory.  This would be better for the "principle of least surprise".

(Another remark on the changes to target libraries: newlib and winsup 
are not affected because they do not special host tools, like fastjar 
for libjava, and neither do they need to access tm.h in the gcc 
directory, like libobjc).

Paolo