baremetal,wasm: support command line params and environment variables

This is mainly useful to be able to run `tinygo test`, for example:

    tinygo test -target=cortex-m-qemu -v math

This is not currently supported, but will be in the future.

src/runtime/runtime_wasm_js.go

@@ -15,11 +15,6 @@ func _start() {
 	run()
 }
 
-//go:linkname syscall_runtime_envs syscall.runtime_envs
-func syscall_runtime_envs() []string {
-	return nil
-}
-
 var handleEvent func()
 
 //go:linkname setEventHandler syscall/js.setEventHandler