internal/testenv: allow "-noopt" anywhere in builder name in test

testenv's TestHasGoBuild test is supposed to allow noopt builders to not
have go build, but the pattern match is failing on the LUCI builders
where a test shard might have an additional "-test_only" suffix in the
builder name. Furthermore, in the LUCI world, "run mods" (the builder
type suffixes) are supposed to be well-defined and composable, so it
doesn't make sense to restrict "-noopt" to the builder suffix anyway.

This change modifies the test to allow "-noopt" to appear anywhere in
the builder name when checking if it's running on a noopt builder.

Change-Id: I393818e3e8e452c7b0927cbc65726d552aa8ff8e
Reviewed-on: https://go-review.googlesource.com/c/go/+/558596
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Bryan Mills <bcmills@google.com>

src/internal/testenv/testenv_test.go

@@ -97,7 +97,7 @@ func TestHasGoBuild(t *testing.T) {
 			}
 		}
 
-		if strings.HasSuffix(b, "-noopt") {
+		if strings.Contains(b, "-noopt") {
 			// The -noopt builder sets GO_GCFLAGS, which causes tests of 'go build' to
 			// be skipped.
 			t.Logf("HasGoBuild is false on %s", b)