os: Chmod: don't test on wasi yet, wasi-libc does not yet support it

Lets "tinygo test -target wasi os" compile, if not pass.

For https://github.com/tinygo-org/tinygo/issues/2369

src/os/os_chmod_test.go

@@ -0,0 +1,27 @@
+// +build !baremetal,!js,!wasi
+
+// TODO: Move this into os_test.go (as upstream has it) when wasi supports chmod
+
+package os_test
+
+import (
+	. "os"
+	"runtime"
+	"testing"
+)
+
+func TestChmod(t *testing.T) {
+	f := newFile("TestChmod", t)
+	defer Remove(f.Name())
+	defer f.Close()
+	// Creation mode is read write
+
+	fm := FileMode(0456)
+	if runtime.GOOS == "windows" {
+		fm = FileMode(0444) // read-only file
+	}
+	if err := Chmod(f.Name(), fm); err != nil {
+		t.Fatalf("chmod %s %#o: %s", f.Name(), fm, err)
+	}
+	checkMode(t, f.Name(), fm)
+}

src/os/os_test.go

@@ -34,22 +34,6 @@ func checkMode(t *testing.T, path string, mode FileMode) {
 	}
 }
 
-func TestChmod(t *testing.T) {
-	f := newFile("TestChmod", t)
-	defer Remove(f.Name())
-	defer f.Close()
-	// Creation mode is read write
-
-	fm := FileMode(0456)
-	if runtime.GOOS == "windows" {
-		fm = FileMode(0444) // read-only file
-	}
-	if err := Chmod(f.Name(), fm); err != nil {
-		t.Fatalf("chmod %s %#o: %s", f.Name(), fm, err)
-	}
-	checkMode(t, f.Name(), fm)
-}
-
 func TestReadAt(t *testing.T) {
 	if runtime.GOOS == "windows" {
 		t.Log("TODO: implement Pread for Windows")