Unclear Configure Options

[booleandomain <booleandomain@xxxxxxxxx>]

Hello,

I'm trying to compile gcc-4.4.0 but I don't understand the meaning of 
some configure options.

For example, what does the --with-local-prefix do? I read you should 
specify a directory, where the default is /usr/local. I also read it is 
not a directory where gcc will install files to, but it is a directory 
gcc will read files from. I wonder what gcc likes to find inside of it. 
I also wonder if it is possible to use something like 
--without-local-prefix.

Another option I don't fully understand is --with-sysroot, that is used 
only when cross-compiling. It also accepts a directory path. What does 
gcc likes to find inside it? Linux kernel headers perhaps? Glibc libraries?

I also don't know if it is possible to delete the specified directories 
after gcc installation, or if gcc must be able to access them even after 
installation has been done.

Thanks.