RE: libm -fno-builtin

>I suggest it still be defaulted but a configuration switch added.
>Platforms can override in configure.host to make their own default or users can experiment with the option turned off/on if desired.
>What builtins are provided for each platform and how well they work and how they will affect the build is unknown at this point.

I tried building libc without -fno-builtin as well, and for my target at least, there weren't too many changes. A couple of things I noticed were:

- strlen etc inlined.
- bzero replaced by call to memset.
- puts changed to fwrite 

Which all seem ok. So attached is a patch to the configure scripts, which I hope is roughly what you have suggested. I've added the configure option --disable-newlib-fno-builtin which prevents -fno-builtin from being used, and it should default to being enabled.

Cheers,
Jon