internal/pkg: cache flags

This is cleaner for extending the API.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/pkg/ir_test.go

@@ -85,7 +85,7 @@ func TestIRRoundtrip(t *testing.T) {
 	testCasesCache := make([]cacheTestCase, len(testCases))
 	for i, tc := range testCases {
 		want := tc.a
-		testCasesCache[i] = cacheTestCase{tc.name, nil,
+		testCasesCache[i] = cacheTestCase{tc.name, 0, nil,
 			func(t *testing.T, base *check.Absolute, c *pkg.Cache) {
 				r, w := io.Pipe()