testing: implement dummy Helper method

This lets a few more packages pass tests: container/heap and
encoding/ascii85.

Makefile

@@ -195,8 +195,10 @@ test: wasi-libc
 # implied -v flag).
 .PHONY: tinygo-test
 tinygo-test:
+	$(TINYGO) test container/heap
 	$(TINYGO) test container/list
 	$(TINYGO) test container/ring
+	$(TINYGO) test encoding/ascii85
 	$(TINYGO) test math
 	$(TINYGO) test text/scanner
 	$(TINYGO) test unicode/utf8

src/testing/testing.go

@@ -42,7 +42,7 @@ type TB interface {
 	SkipNow()
 	Skipf(format string, args ...interface{})
 	Skipped() bool
-	// Helper()
+	Helper()
 }
 
 var _ TB = (*T)(nil)
@@ -154,6 +154,11 @@ func (c *common) Skipped() bool {
 	return c.skipped
 }
 
+// Helper is not implemented, it is only provided for compatibility.
+func (c *common) Helper() {
+	// Unimplemented.
+}
+
 // InternalTest is a reference to a test that should be called during a test suite run.
 type InternalTest struct {
 	Name string