build-infra: warning: [path] bad path element on Solaris

When compiling on Solaris (I think it's for all CPUs, but check the Tendril logs), we get several warnings like this:
Compiling 5 files for BUILD_DEMO_Stylepad
warning: [path] bad path element "/export/HUDSON/workspace/2-build-solaris-sparc@2/jdk8-newmake/1571/build/solaris-sparc/jdk/lib/jconsole.jar": no such file or directory

We should not have warnings from build-infra that are introduced by the build system. This should be fixed.