toolchain installtion/usage issue

[chchenl]

Hi,
Is this repo used to replace the gcc directory in the default downloaded repo such as
riscv-gnu-toolchain/gcc, while keeping other portions of riscv-gnu-toolchain untouched?

Also, in configuring the toolchain for a build, what shoud be set for '-march', '-mabi', and other such options?
Or rather, is there any documention on how to stitch this repo with the downloaded riscv-gnu-toolchain?
I cannot find info on how to make use of this corev-gcc repo.

Thanks for info.
--vincent