Restarting make

[Perry Smith <pedz@xxxxxxxxxxxxxxxx>]

I'm mucking about trying to build gcc in a weird way.  I added code  
to a file in libstdc++/libsupc which caused the make to error off.   
So I can fix my mistake in the c code.  But how do I restart the  
build from where it left off?  I only know that "make bootstrap"  
builds everything.  And from what I can tell, it rebuilds everything  
even if it already exists.  (Or am I mistaken about that?)

Thank you,
Perry Smith