GitLab

build/toolchains/<name>/*                    --> toolchains/<name>/*
build/prebuilt/<system>/<name>/lib/gdbserver --> toolchains/<name>/prebuilt/gdbserver
build/prebuilt/<system>/<name>/              --> toolchains/<name>/prebuilt/<system>/

The main idea is to group all toolchain-related files under the same directory.

Change-Id: Idb41de49b5d81b6881ac4e0eea24506ff4a07f03