Can I build gcc so -Wall option is always on ?

[Dr. David Kirkby]

I'm helping on the Sage maths project

http://www.sagemath.org/

where there are a large number of packages built, most of which ignore CFLAGS. 
(Quite a few ignore CC and CXX too!) I'd like to display all the warnings, but 
its hard when people overwrite CFLAGS.

Is there a way I can build gcc such that effectively "-Wall" is enabled all the 
time?

If not, could anyone point me to where in the source code I might be able to 
hack it, to build a version which displays all the warnings?

I think it would actually be quite a useful option to have when one configures gcc!

i.e

configure --prefix=/some/dir --always-display-all-warnings !!!


Dave