fix Jar execution on Java 11

[monperrus]

Problem

One cannot use the Jar in Java 11, this crashes as follows, see bug report from @layornos

$ java -jar target/spoon-core-8.4.0-SNAPSHOT-jar-with-dependencies.jar 
Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/logging/log4j/util/StackLocator$FqcnCallerLocator
	at org.apache.logging.log4j.util.StackLocator.<clinit>(StackLocator.java:37)
	at org.apache.logging.log4j.util.StackLocatorUtil.<clinit>(StackLocatorUtil.java:33)
	at org.apache.logging.log4j.LogManager.getLogger(LogManager.java:588)
	at spoon.Launcher.<clinit>(Launcher.java:589)
Caused by: java.lang.ClassNotFoundException: org.apache.logging.log4j.util.StackLocator$FqcnCallerLocator
	at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:581)
	at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:178)
	at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:522)
	... 4 more

Root cause

Log4J works poorly on Java 11, and requires a multi-release mode, see https://stackoverflow.com/questions/53049346/is-log4j2-compatible-with-java-11

Fix

add the multi-release info in the manifest

Thougts: we may want to move away from Log4J.

[nharrand]

Thougts: we may want to move away from Log4J.

I agree.

[MartinWitt]

We can open a separate issue if needed but i hijack the merged pr for the discussion for now.

Thougts: we may want to move away from Log4J.

Before we make this change, is the performance impact from log4j jdk11 significant to earlier jdks?
Because I don't know a lot of good java logging frameworks . Do you have any replacement in mind?
Logging frameworks:

• java.util.Logger (slow and bad)
• https://github.com/google/flogger (early and google product)
• log4j2/sl4j
• logback

[monperrus]

SLF4J is a great API, with many backends.

Since we have Spoon, we could write a transformation to automatically migrate from the log4j API to the SLF4J API... and apply the transformation to Spoon itself. A little bit like http://www.slf4j.org/migrator.html, but much more complete.