Should i compile newlib after

[Paul Chavent]

Hello.
I am building a cross-compile toolchain for an arm7tdmi (gameboy). I 
would like to know if it is usefull to 'configure' and 'make all 
install' for newlib if i have compiled gcc with the '--with-newlib' and 
i have copy the newlib directory in gcc sources ?
If it is usefull, what is it used for ?
And, sometimes, we see some people recompile gcc after newlib ?
Is it usefull and what is it used for ?

Thank you.

Happy new year.

Paul.