I tried to do my homework but didn't see any other issue in the issue tracker with Weld as the project and "sun misc Unsafe" as search keywords. Feel free to close if this is a duplicate.
ClassUtils.java line 75 features a blind invocation of sun.misc.Unsafe that throws a NoClassDefFoundError under JDK 11. Here's the source link: https://github.com/weld/core/blob/8d4fb65fcba96a41abbf8c019f8162a786cc1435/impl/src/main/java/org/jboss/weld/util/bytecode/ClassFileUtils.java#L75
It's my understanding that Unsafe is no longer present in JDK 11.
We stumbled across this when a user mistakenly used the module path in case it matters.