[CI] Workaround for Windows packaging tests hang on uploading artifacts (elastic#137206)

Calculate upload timeout based on file size. This change replaces the
fixed 30-minute timeout with a calculated value, to avoid
buildkite-agent on Windows hanging for 30 minutes for small files.

Author: jozala

build-tools-internal/src/main/java/org/elasticsearch/gradle/internal/ElasticsearchBuildCompletePlugin.java

@@ -48,6 +48,7 @@
 import java.util.Arrays;
 import java.util.List;
 import java.util.Optional;
+import java.util.concurrent.TimeUnit;
 
 import javax.inject.Inject;
 
@@ -199,7 +200,11 @@ public void execute(BuildFinishedFlowAction.Parameters parameters) throws FileNo
                     try {
                         // we are very generious here, as the upload can take
                         // a long time depending on its size
-                        pb.start().waitFor(30, java.util.concurrent.TimeUnit.MINUTES);
+                        long timeoutSec = calculateUploadWaitTimeoutSeconds(uploadFile);
+                        boolean completedInTime = pb.start().waitFor(timeoutSec, TimeUnit.SECONDS);
+                        if (completedInTime == false) {
+                            System.out.println("Timed out waiting for buildkite artifact upload after " + timeoutSec + " seconds");
+                        }
                     } catch (InterruptedException e) {
                         System.out.println("Failed to upload buildkite artifact " + e.getMessage());
                     }
@@ -304,5 +309,14 @@ private static String calculateArchivePath(Path path, Path projectPath) {
             }
             return archivePath;
         }
+
+        private static long calculateUploadWaitTimeoutSeconds(File file) {
+            long fileSizeBytes = file.length();
+            long fileSizeMB = fileSizeBytes / (1024 * 1024);
+
+            // Allocate 4 seconds per MB (assumes ~250 KB/s upload speed)
+            // with min 10 seconds and max 30 minutes
+            return Math.max(10, Math.min(1800, fileSizeMB * 4));
+        }
     }
 }