"make bubblestrap" weirdness

[Kelley Cook]

> In recent CVS checkouts of GCC mainline, I have noticed a
> weird bootstrapping issue. The steps are:
> 
>   1. make bootstrap
>   2. touch $GCC_SRC_DIR/gcc/java/check-init.c
>   3. make bubblestrap
>   4. touch $GCC_SRC_DIR/gcc/java/check-init.c
>   5. make bubblestrap
> 
> In step #3, I see "genattrab" and other "gen*" programs
> running once again, while in #5 (and subsequent such
> iterations) they don't. I have seen this on two separate
> x86-Linux boxen.

It seems that you've discovered a regression from 3.4.  Unfortunately, 
it likely is related to my moving the GCC build executables into a 
build/ directory.

Please create a new PR and feel free to assign it to me <kcook@gcc.gnu.org>.