scripts: Update riscv-toolchain install script to support CI
scripts: Update riscv-toolchain install script to support CI

If the tarball is preinstalled (as in the CI docker image), bypass the
fetch and only extract the tarball the cache toolchain location.

Change-Id: I2eca45980671ef9435340c3567d99910665b56a4
GitOrigin-RevId: 60e7b5ea6cab9e5652b834ba8fef2d4c9fa6a18e

AmbiML/sparrow-scripts-full,AmbiML/sparrow-scripts-full