all: replace target=wasi with target=wasip1

This eliminates the 'wasi' build tag in favor of 'GOOS=wasip1', introduced in Go 1.21.

For backwards compatablity, -target=wasi is a synonym for -target=wasip1.

main.go

@@ -285,7 +285,7 @@ func Test(pkgName string, stdout, stderr io.Writer, options *compileopts.Options
 		// Tests are always run in the package directory.
 		cmd.Dir = result.MainDir
 
-		// wasmtime is the default emulator used for `-target=wasi`. wasmtime
+		// wasmtime is the default emulator used for `-target=wasip1`. wasmtime
 		// is a WebAssembly runtime CLI with WASI enabled by default. However,
 		// only stdio are allowed by default. For example, while STDOUT routes
 		// to the host, other files don't. It also does not inherit environment
@@ -1548,6 +1548,11 @@ func main() {
 		options.PrintCommands = printCommand
 	}
 
+	// Compatibility with legacy -target=wasi
+	if options.Target == "wasi" {
+		options.Target = "wasip1"
+	}
+
 	err = options.Verify()
 	if err != nil {
 		fmt.Fprintln(os.Stderr, err.Error())