Changed

• Changed launch subcommand to exit with the exit status of the launched command so that failing exit codes are propagated to the calling process.
• Changed launch --shell to provide a --norc flag (or the equivalent) for bash, zsh and pwsh so that the user does not accidentally mess up the environment.
• Changed launch --shell to fail if the user's SHELL environment variable is not valid UTF-8, instead of defaulting to bash.
• The default toolchain is now updated during installs to the requested version, rather than the newest version for the corresponding toolchain.