Can't build kie-wb-webapp 6.1.x (JBPM) - gwt

Question

I need to modify KIE Workbench source and I have two issues that are stopping me from building with Maven 3.2.5, one on Windows and one on Linux.
On Windows 7, I am getting an error that says
[deletia...]SNAPSHOT\uberfire-backend-api-0.4.0-SNAPSHOT-sources.jar,
com.google.gwt.dev.Compiler,-logLevel, INFO, -style, OBF, -war,
c:\kie-wb-webapp\target\kie-wb-webapp-6.1.1-SNAPSHOT, -localWorkers, 1,
-strict, -XfragmentCount, -1, -deploy, c:\kie-wb-webapp\target\gwt-symbols-deploy, -gen,
c:\kie-wb-webapp\target\.generated, org.kie.workbench.FastCompiledKIEWebapp]:
Error while executing process. Cannot run program "c:\development\software\jdk\jdk1.7.0_71\jre\bin\java":
CreateProcess error=206, The filename or extension is too long.
So I looked it up and apparently, this is well known limitation since gwt-maven-plugin creates a command-line that is longer than 8191 chars and this is forbidden. So I gave it a shot on Ubuntu.
On Ubuntu,
I am getting:
[INFO] --- gwt-maven-plugin:2.5.1:compile (gwt-compile) # kie-wb-webapp [ERROR] Java HotSpot(TM) 64-Bit Server VM warning: ignoring option MaxPermSize=256m; support was removed in 8.0
[ERROR] Java HotSpot(TM) 64-Bit Server VM warning: ignoring option PermSize=128m; support was removed in 8.0
[INFO] Compiling module org.kie.workbench.FastCompiledKIEWebapp
[INFO] Validating units:
[INFO] [ERROR] Errors in 'jar:file:/home/rich/.m2/repository/com/google/guava/guava-gwt/14.0.1/guava-gwt-14.0.1.jar!/com/google/common/primitives/Booleans.java'
[INFO] [ERROR] Line 29: The import java.util.BitSet cannot be resolved
[INFO] [ERROR] Aborting compile due to errors in some input files
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE*
It's really important that I find a workaround to 1 or both of these issues (my guess is that if I clear the command-line issue on Windows, I'll just run into the guava issue again). Also, unless it's absolutely necessary, I can't upgrade to 6.2.x, because this would cause a lot of work for my project.
Has anyone run into this?

Answer 1

If you don't need Java 8 support, you may be able to solve the problem by using an earlier version of the JDK. I believe that you do this by setting JAVA_HOME for your Maven run. You can download a JDK 7 here.
You could also build Guava yourself from HEAD, as the problem has been fixed there but not included in a release. Or you could wait for a 19.0-rc1, which we hope to have out soon.