Fix escape \\

Jenkinsfile

@@ -8,10 +8,10 @@
             sh 'javac -cp "./src" -d "./bin" $(find . -iname "*.java" -type f) -Xlint:deprecation'
             sh 'echo "BUILDING CLIENT"'
             sh 'echo Main-Class: clientP2P/ClientP2P > MANIFEST.MF'
-            sh 'jar -cvmf MANIFEST.MF client.jar $(find . \( -iname "*.class" -and ! -iwholename "*/clientP2P/*.class" \) -type f)'
+            sh 'jar -cvmf MANIFEST.MF client.jar $(find . \\( -iname "*.class" -and ! -iwholename "*/clientP2P/*.class" \\) -type f)'
             sh 'echo "BUILDING SERVER"'
             sh 'echo Main-Class: javaProjet2020/Server > MANIFEST.MF'
-            sh 'jar -cvmf MANIFEST.MF server.jar $(find . \( -iname "*.class" -and ! -iwholename "*/serverP2P/*.class" \) -type f)'
+            sh 'jar -cvmf MANIFEST.MF server.jar $(find . \\( -iname "*.class" -and ! -iwholename "*/serverP2P/*.class" \\) -type f)'
             sh 'tar -zcvf sources.tar.gz src/'
           }
         }