cmd/cgo/internal/testsanitizers: check for go build and cgo in fuzzer and msan tests

Make sure the platform we are running the tests on can compile programs
and has cgo support in order to run the fuzzer and msan tests. This is the
same approach used by the asan tests, which share the same requirements.

Fixes #64626

Change-Id: I7c0b912dabdd1b7d7d44437e4ade5e5994994796
GitHub-Last-Rev: 9fae6970f0
GitHub-Pull-Request: golang/go#64640
Reviewed-on: https://go-review.googlesource.com/c/go/+/548715
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Bryan Mills <bcmills@google.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>

src/cmd/cgo/internal/testsanitizers/libfuzzer_test.go

@@ -7,11 +7,14 @@
 package sanitizers_test
 
 import (
+	"internal/testenv"
 	"strings"
 	"testing"
 )
 
 func TestLibFuzzer(t *testing.T) {
+	testenv.MustHaveGoBuild(t)
+	testenv.MustHaveCGO(t)
 	goos, err := goEnv("GOOS")
 	if err != nil {
 		t.Fatal(err)

src/cmd/cgo/internal/testsanitizers/msan_test.go

@@ -8,11 +8,14 @@ package sanitizers_test
 
 import (
 	"internal/platform"
+	"internal/testenv"
 	"strings"
 	"testing"
 )
 
 func TestMSAN(t *testing.T) {
+	testenv.MustHaveGoBuild(t)
+	testenv.MustHaveCGO(t)
 	goos, err := goEnv("GOOS")
 	if err != nil {
 		t.Fatal(err)