See LFS for build instructions, ref. post # 2.
http://archive.linuxfromscratch.org/lfs-museum/
Requirements to build a tool chain, etc. :
LFS, Minimum ""Host System Requirements""
http://archive.linuxfromscratch.org/.../hostreqs.html
I.e. all twenty "packages".
Most questions will be answered by reading the LFS books :
Which version is required for which version, etc. etc.
And better read about what a kernel is and does.
Objects that are build with gcc will depend on the version
of glibc ( or a later version ) used at build time.
Unless you understand it all in depth, you will not
be able to build a tool chain for another Linux.
The recommended way is to build LFS ( a couple of times ).
And then later move on to CLFS, Cross Linux From Scratch.
To find out, how all things are connected.
.....