Add RISC-V GNU/Linux to src/tools/build-manifest as a host platform
Add RISC-V GNU/Linux to src/tools/build-manifest as a host platform

graydon/rust,graydon/rust,graydon/rust,aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,aidancully/rust,aidancully/rust