This patch is a "definitive" solution to the problem of building gcc 
in-srcdir.  It builds host modules out of srcdir always, so that they do 
not conflict with the configuration of build or target modules.  For an 
out-of-srcdir build, this does not change anything, but when --srcdir=. 
gcc will be configured to for example host-i686-pc-linux-gnu/gcc, ld 
will be configured to for example host-i686-pc-linux-gnu/ld, etc.

While this can be even expected for gcc, which anyway is almost always 
built out-of-srcdir, it may violate the "principle of least surprise" 
for binutils or gdb.  In that case, --srcdir=. is ok.  That's why I am 
posting to all three lists.

The patch requires some changes in target libraries to be able to find 
the newly-built gcc, but this is not necessary in src packages.

I bootstrapped/regtested GCC (in-srcdir and out-of-srcdir) and 
built/regtested the gdb+binutils src module in-srcdir with this patch.

Ok for gcc and src?

Paolo