build: Update riscv toolchain build config
build: Update riscv toolchain build config

Need to specify ISA version to resolve GNU/LLVM misalignment

Bump the build speed for local test and CI

Change-Id: Ied5eaac13308ffe49b467ca2f0cdcaf4c8cbfcc3
GitOrigin-RevId: 535548b13c87dcc73bdf7be5b2198a3d9768cfca

AmbiML/sparrow-build