testing/kubectl-krew: fix tests due to lingering index cache

> --- FAIL: TestKrewUpdateListsUpgradesAvailable (1.82s)
> [..]
> update_test.go:129: output should not mention update available for "ns"; output=Updated the local copy of plugin index.
> [..]
> FAIL
> FAIL	sigs.k8s.io/krew/integration_test	70.448s

testing/kubectl-krew/APKBUILD

@@ -8,7 +8,10 @@ arch="all !armhf !riscv64" # kubectl
 license="Apache-2.0"
 depends="kubectl"
 makedepends="go"
-source="$pkgname-$pkgver.tar.gz::https://github.com/kubernetes-sigs/krew/archive/refs/tags/v$pkgver.tar.gz"
+source="
+	$pkgname-$pkgver.tar.gz::https://github.com/kubernetes-sigs/krew/archive/refs/tags/v$pkgver.tar.gz
+	test-use-testing-tmpdir.patch
+	"
 builddir="$srcdir/krew-$pkgver"
 
 export GOCACHE="${GOCACHE:-"$srcdir/go-cache"}"
@@ -35,4 +38,5 @@ package() {
 
 sha512sums="
 888362c564500d3f9f00b3207f5d63ee6546f9da6c884736fa55d49e78b91d5085a518f69f41b156cc8dc13667846be98bc2459392ca3d970c89721b6f4b632b  kubectl-krew-0.4.4.tar.gz
+797a0f1361d893289217569e09dd5564fe545eaf2f0b3dc40367c63cb124b8120c5600d190732ced7885a020ae56a9417b49bccb8bca2c87faf72bf3e1359a81  test-use-testing-tmpdir.patch
 "

testing/kubectl-krew/test-use-testing-tmpdir.patch

@@ -0,0 +1,15 @@
+Outdated index files from previous builds break tests. Use t.TempDir() to make
+sure a new index file is used.
+diff --git a/integration_test/testutil_test.go b/integration_test/testutil_test.go
+index 66ebc98..d91635b 100644
+--- a/integration_test/testutil_test.go
++++ b/integration_test/testutil_test.go
+@@ -277,7 +277,7 @@ func (it *ITest) loadReceipt(path string) index.Receipt {
+ // It caches the index tree as in-memory tar after the first run.
+ func (it *ITest) initializeIndex() {
+ 	initIndexOnce.Do(func() {
+-		persistentCacheFile := filepath.Join(os.TempDir(), persistentIndexCache)
++		persistentCacheFile := filepath.Join(it.t.TempDir(), persistentIndexCache)
+ 		fileInfo, err := os.Stat(persistentCacheFile)
+ 
+ 		if err == nil && fileInfo.Mode().IsRegular() {