About the procedure of fixinclude in building gcc

["Cheng bin" <amker dot cheng at gmail dot com>]

Hi All:
     Now I am working on the procedure of fixinclude in building gcc
and got following concepts.
Take three PATH as example to illustrate,
     ginclude    : which provided by gcc source includes system
headers wanted by gcc;
     sys_inc     : the location of system header files;
     local         : the locattion for system headers fixed by gcc;

When building gcc, there are two steps to finish the job of fixing headers:
STEP1:    fixinc.sh will fix system headers in PATH: sys_inc and put
fixed ones into
               PATH:local ;
STEP2:    gcc(actually is building makefiles) will copy all files from
PATH:ginclude to
               PATH:local. In this step, it will copy anything into
PATH:local even if there
               is one as the result of STEP1.

After all, gcc will search system headers in PATH:local firstly and
then in PATH:sys_inc.

I'am not sure about my comprehension, am I right?

And there is a question about ./fixincludes/Makefile.
I think the gcc's top level Makefile will configure fixincludes and
create that Makefile,
and then will do such "make ./fixincludes/Makefile" thing, But I found
following rules in
./fixincludes/Makefile:

all : oneprocess fixinc.sh mkheaders
fixinc.sh : fixinc.in mkfixinc.sh Makefile
	(commands to create fixinc.sh)
Makefile: $(srcdir)/Makefile.in config.status
	$(SHELL) ./config.status Makefile

Look at the last rule with target Makefile, does it recreate exactly
this Makefile recursively?
 And why doing this?
I have to admit that I know nothing about config.status except
comments say that it is used
to recreate the current configuration.

Thanks for look at this message, and any suggestion will be greatly appreciated!