cmd/go: convert TestIssue12096 to the script framework

Part of converting all tests to script framework to improve
test parallelism.

Updates #36320
Updates #17751

Change-Id: I27e52c4eabfcd1782965f17c098719dd0ea7e3ca
Reviewed-on: https://go-review.googlesource.com/c/go/+/214390
Reviewed-by: Jay Conrod <jayconrod@google.com>

src/cmd/go/go_test.go

@@ -2189,21 +2189,6 @@ func TestIssue11709(t *testing.T) {
 	tg.run("run", tg.path("run.go"))
 }
 
-func TestIssue12096(t *testing.T) {
-	tg := testgo(t)
-	defer tg.cleanup()
-	tg.tempFile("test_test.go", `
-		package main
-		import ("os"; "testing")
-		func TestEnv(t *testing.T) {
-			if os.Getenv("TERM") != "" {
-				t.Fatal("TERM is set")
-			}
-		}`)
-	tg.unsetenv("TERM")
-	tg.run("test", tg.path("test_test.go"))
-}
-
 func TestGoBuildARM(t *testing.T) {
 	if testing.Short() {
 		t.Skip("skipping cross-compile in short mode")

src/cmd/go/testdata/script/test_env_term.txt

@@ -0,0 +1,15 @@
+# Tests golang.org/issue/12096
+
+env TERM=''
+go test test_test.go
+! stdout '^ok.*\[no tests to run\]'
+stdout '^ok'
+
+-- test_test.go --
+package main
+import ("os"; "testing")
+func TestEnv(t *testing.T) {
+	if os.Getenv("TERM") != "" {
+		t.Fatal("TERM is set")
+	}
+}