Update MdcSerializerResolver.java (#321)

Author: jackshirazi

log4j2-ecs-layout/src/main/java/co/elastic/logging/log4j2/MdcSerializerResolver.java

@@ -40,7 +40,7 @@ static MdcSerializer resolve(String mdcSerializerFullClassName) {
             Class<?> clazz = Class.forName(mdcSerializerFullClassName);
             return (MdcSerializer) clazz.getDeclaredConstructor().newInstance();
         } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | NoSuchMethodException |
-                 InvocationTargetException e) {
+                 InvocationTargetException | RuntimeException e) { //RuntimeException added because of bizarre build issue
             throw new IllegalArgumentException("Could not create MdcSerializer " + mdcSerializerFullClassName, e);
         }
     }