Only check copy rules into the snapshot directory

Test: m nothing
Change-Id: I6d9ab5a9f003193c5791a4ee6d3ee35730ddf96c
diff --git a/sdk/testing.go b/sdk/testing.go
index be882d4..3ae8b5d 100644
--- a/sdk/testing.go
+++ b/sdk/testing.go
@@ -188,15 +188,20 @@
 
 	buildParams := sdk.BuildParamsForTests()
 	copyRules := &strings.Builder{}
+	snapshotDirPrefix := sdk.builderForTests.snapshotDir.String() + "/"
 	for _, bp := range buildParams {
 		switch bp.Rule.String() {
 		case android.Cp.String():
-			// Get source relative to build directory.
-			src := android.NormalizePathForTesting(bp.Input)
-			// Get destination relative to the snapshot root
-			dest := bp.Output.Rel()
-			_, _ = fmt.Fprintf(copyRules, "%s -> %s\n", src, dest)
-			info.snapshotContents = append(info.snapshotContents, dest)
+			output := bp.Output
+			// Only check copies into the snapshot directory.
+			if strings.HasPrefix(output.String(), snapshotDirPrefix) {
+				// Get source relative to build directory.
+				src := android.NormalizePathForTesting(bp.Input)
+				// Get destination relative to the snapshot root
+				dest := output.Rel()
+				_, _ = fmt.Fprintf(copyRules, "%s -> %s\n", src, dest)
+				info.snapshotContents = append(info.snapshotContents, dest)
+			}
 
 		case repackageZip.String():
 			// Add the destdir to the snapshot contents as that is effectively where