--target= carries a value, so the flag test becomes a prefix match and the
residual-argument filter uses the same test — otherwise -o out --target=X fell
into the usage error. A wasm build defaults to a .wasm name, since the
extension is what tells a runtime, and a reader, what the file is.
flan run refuses the flag by name. It builds and execs, a cross-built module is
not something this host execs, and choosing a runtime for it is not a decision
this command should be making quietly.
Joseph Ferano
48a7186c58