Don't rely on external jar command to amend jar files' manifests

build.java

@@ -1,5 +1,4 @@
 import java.io.File;
-import java.io.FileWriter;
 import java.io.IOException;
 import java.nio.charset.StandardCharsets;
 import java.nio.file.FileSystems;
@@ -562,16 +561,8 @@ void build(Options options) throws IOException
                     LOG.debugf("Build Mandrel's wrapper jar...");
                     Mx.BuildArgs buildArgs = Mx.BuildArgs.of("--only", "MANDREL_PACKAGING_WRAPPER");
                     exec.exec.accept(Mx.mxbuild(options, fs.mxHome(), fs.mandrelRepo(), os.javaHome()).apply(buildArgs));
-                    // Add Specification-Version and Implementation-Version to jars' manifests.
-                    // These attributes are access by Red Hat Build of Quarkus to verify that the correct artifacts are being used.
-                    // The value of Specification-Version is not that important, but the Implementation-Version should match the version of the native-image.
                     LOG.debugf("Patch jars' manifests with Specification-Version and Implementation-Version...");
-                    File manifest = createTempManifest(options);
-                    mx.artifacts.forEach((artifact, paths) ->
-                    {
-                        final String jarPath = PathFinder.getFirstExisting(fs.mandrelRepo().resolve(paths[0]).toString(), artifact).toString();
-                        exec.exec.accept(Tasks.Exec.of(List.of("jar", "uvfm", jarPath, manifest.getPath()), fs.mandrelRepo()));
-                    });
+                    mx.artifacts.forEach(amendOrCreateManifest(options, replace));
                     LOG.debugf("Deploy maven artifacts...");
                     Mx.mavenDeploy(options, exec, fs.mxHome(), fs.mandrelRepo(), os.javaHome());
                 }
@@ -587,18 +578,48 @@ void build(Options options) throws IOException
         }
     }
 
-    private File createTempManifest(Options options) throws IOException
+    private BiConsumer<String, Path[]> amendOrCreateManifest(Options options, Tasks.FileReplace.Effects replace)
     {
-        File manifest = File.createTempFile("manifest", "mf");
-        manifest.deleteOnExit();
-        try (FileWriter manifestWriter = new FileWriter(manifest))
+        return (artifact, paths) ->
         {
-            manifestWriter.write("Specification-Version: 0.0\n");
-            manifestWriter.write("Implementation-Version: " + options.mavenVersion + "\n");
-            manifestWriter.flush();
-        }
-        return manifest;
+            final Path jarPath = PathFinder.getFirstExisting(fs.mandrelRepo().resolve(paths[0]).toString(), artifact);
+            try (java.nio.file.FileSystem jarfs = FileSystems.newFileSystem(jarPath, this.getClass().getClassLoader()))
+            {
+                Path metaInfPath = jarfs.getPath("/META-INF");
+                Path manifestPath = metaInfPath.resolve("MANIFEST.MF");
+                if (!Files.exists(manifestPath))
+                {
+                    if (!Files.exists(metaInfPath))
+                    {
+                        Files.createDirectory(metaInfPath);
+                    }
+                    Files.createFile(manifestPath);
+                }
+                Tasks.FileReplace.replace(new Tasks.FileReplace(manifestPath, amendManifest(options)), replace);
+            }
+            catch (IOException e)
+            {
+                throw new RuntimeException(e);
+            }
+        };
+    }
+
+    /*
+     * Add Specification-Version and Implementation-Version to jars' manifests.
+     * These attributes are accessed by Red Hat Build of Quarkus to verify that the correct artifacts are being used.
+     * The value of Specification-Version is not that important, but the Implementation-Version should match the version of the native-image.
+     */
+    private static Function<Stream<String>, List<String>> amendManifest(Options options)
+    {
+        return lines ->
+        {
+            List<String> result = lines.collect(Collectors.toList());
+            result.add("Specification-Version: 0.0");
+            result.add("Implementation-Version: " + options.mavenVersion);
+            return result;
+        };
     }
+
 }
 
 class EnvVar