provisioner/local-exec: Make "stop" test actually useful on Windows

The changes in the previous commit confirmed that this test was passing
only as a false-positive when running on Windows, because the test was
previously only checking that the provisioner was stopped shortly after
asking it to stop, but that wasn't accounting for the possibility that it
stopped due to an unrelated error.

Windows Command Interpreter does not support semicolon as a command
separator, so on Windows we need to use an ampersand instead.

Signed-off-by: Martin Atkins <mart@degeneration.co.uk>

internal/builtin/provisioners/local-exec/resource_provisioner_test.go

@@ -58,10 +58,17 @@ func TestResourceProvider_stop(t *testing.T) {
 	p := New()
 	schema := p.GetSchema().Provisioner
 
+	command := "sleep 30; sleep 30"
+	if runtime.GOOS == "windows" {
+		// On Windows the local-exec provisioner uses cmd.exe by default,
+		// and that uses "&" as a command separator instead of ";".
+		command = "sleep 30 & sleep 30"
+	}
+
 	c, err := schema.CoerceValue(cty.ObjectVal(map[string]cty.Value{
 		// bash/zsh/ksh will exec a single command in the same process. This
 		// makes certain there's a subprocess in the shell.
-		"command": cty.StringVal("sleep 30; sleep 30"),
+		"command": cty.StringVal(command),
 	}))
 	if err != nil {
 		t.Fatal(err)