Comma separation in <excludeFilterFile>not working

[EPluribusUnum]

Hi!

This states, that comma separation shoudl work in : spotbugs/discuss#46
But it uses just the last file, not all defined files.

spotbug maven plugin version : 3.1.12.2

[EPluribusUnum]

debug output of maven. You can see, it gets two different FindBugsExclude.xml files from the pom.xml, but it just uses the last one twice.

`[DEBUG] Spotbugs arg is -xml:withMessages
[DEBUG] Spotbugs arg is -auxclasspathFromInput
[DEBUG] Spotbugs arg is -projectName
[DEBUG] Spotbugs arg is Online Számla
[DEBUG] Spotbugs arg is -effort:max
[DEBUG] Spotbugs arg is -low
[DEBUG] Spotbugs arg is -progress
[DEBUG] Spotbugs arg is -nested:false
[DEBUG] Spotbugs arg is -exclude
[DEBUG] Spotbugs arg is /home/amolnar/Data/projects/navservices/NAVOnlineSzamla/hu.libra.navservices.onlineszamla/target/FindBugsExclude.xml
[DEBUG] Spotbugs arg is -exclude
[DEBUG] Spotbugs arg is /home/amolnar/Data/projects/navservices/NAVOnlineSzamla/hu.libra.navservices.onlineszamla/target/FindBugsExclude.xml
[DEBUG] Spotbugs arg is -output
[DEBUG] Spotbugs arg is /home/amolnar/Data/projects/navservices/NAVOnlineSzamla/hu.libra.navservices.onlineszamla/target/spotbugsTemp.xml
[DEBUG] Spotbugs arg is /home/amolnar/Data/projects/navservices/NAVOnlineSzamla/hu.libra.navservices.onlineszamla/target/classes
[java] Scanning archives
...
[DEBUG] (s) classFilesDirectory = /home/amolnar/Data/projects/navservices/NAVOnlineSzamla/hu.libra.navservices.onlineszamla/target/classes
[DEBUG] (s) compileSourceRoots = [/home/amolnar/Data/projects/navservices/NAVOnlineSzamla/hu.libra.navservices.onlineszamla/src/main/java, /home/amolnar/Data/projects/navservices/NAVOnlineSzamla/hu.libra.navservices.onlineszamla/target/generated-sources/cxf]
[DEBUG] (s) debug = true
[DEBUG] (s) effort = Max
[DEBUG] (s) excludeFilterFile = /home/amolnar/.m2/repository/hu/libra/sporbugs-root/1.0.0/FindBugsExclude.xml,/home/amolnar/Data/projects/navservices/NAVOnlineSzamla/hu.libra.navservices.onlineszamla/FindBugsExclude.xml
[DEBUG] (s) failOnError = true
...

`