Patch: automatic dependencies for gcc

[Andreas Tobler]

Tom Tromey wrote:

> Ralf> Another thing: have you tried a parallel (make -jN) build with this on a
> Ralf> multi-way system?
> 
> Yes, I've done a number of -j4 bootstraps on the compile farm machine
> gcc11.  That is a 4 CPU x86-64 machine.

Do also bootstraps with N > # of cpus/cores. I fail on a 2x2 core with a 
-j6.

Thanks for the Work Tom!
Andreas