add jetty-project 12.1.0.alpha1

https://github.com/jvm-repo-rebuild/reproducible-central/blob/master/content/org/eclipse/jetty/jetty-project/README.md

content/org/eclipse/jetty/jetty-project/jetty-project-12.1.0.alpha1.buildspec

@@ -0,0 +1,19 @@
+groupId=org.eclipse.jetty
+artifactId=jetty-project
+display=${groupId}:${artifactId}
+version=12.1.0.alpha1
+
+gitRepo=https://github.com/eclipse/jetty.project.git
+gitTag=jetty-${version}
+
+tool=mvn-3.9.6
+jdk=22
+newline=lf
+umask=002
+
+timestamp=1734977518436 # extracted from: wget https://repo.maven.apache.org/maven2/org/eclipse/jetty/jetty-util/$version/jetty-util-$version.jar ; unzip -q -c jetty-util-$version.jar org/eclipse/jetty/version/build.properties | grep timestamp
+command="mvn -Peclipse-release clean package -DskipTests -Dgpg.skip -Dtimestamp=${timestamp} -Dbuildinfo.ignore=*/*-p2site.zip"
+buildinfo=target/${artifactId}-${version}.buildinfo
+
+#diffoscope=${artifactId}-${version}.diffoscope
+issue=