v0.12: Fix tests for Moby v25 compatibility

- Skip testSchema1Image: gcr.io no longer supports Schema1 manifests
- Update Alpine pins from 3.18 to 3.20 with current digests

These changes ensure buildkit v0.12 tests pass with Moby v25.

Signed-off-by: Shubhranshu Mahapatra <shubhum@amazon.com>

Author: Shubhranshu153

client/client_test.go

@@ -6131,6 +6131,7 @@ func testMoveParentDir(t *testing.T, sb integration.Sandbox) {
 
 // #296
 func testSchema1Image(t *testing.T, sb integration.Sandbox) {
+	t.Skip("gcr.io no longer supports Schema1 manifests")
 	c, err := New(sb.Context(), sb.Address())
 	require.NoError(t, err)
 	defer c.Close()

util/testutil/integration/pins.go

@@ -7,10 +7,10 @@ var pins = map[string]map[string]string{
 		"arm64v8": "sha256:1fa89c01cd0473cedbd1a470abb8c139eeb80920edf1bc55de87851bfb63ea11",
 		"library": "sha256:3fbc632167424a6d997e74f52b878d7cc478225cffac6bc977eedfe51c7f4e79",
 	},
-	// alpine 3.18
+	// alpine 3.20
 	"alpine:latest": {
-		"amd64":   "sha256:25fad2a32ad1f6f510e528448ae1ec69a28ef81916a004d3629874104f8a7f70",
-		"arm64v8": "sha256:e3bd82196e98898cae9fe7fbfd6e2436530485974dc4fb3b7ddb69134eda2407",
-		"library": "sha256:82d1e9d7ed48a7523bdebc18cf6290bdb97b82302a8a9c27d4fe885949ea94d1",
+		"amd64":   "sha256:b0cb30c51c47cdfde647364301758b14c335dea2fddc9490d4f007d67ecb2538",
+		"arm64v8": "sha256:9ace55212059e43b0b246bb975a26b4f6fb41f7384bc87b57ad3aae2a6e5e817",
+		"library": "sha256:a4f4213abb84c497377b8544c81b3564f313746700372ec4fe84653e4fb03805",
 	},
 }