Improved: fix a PDF generation issue with Buildbot too now

Before only Windows was concerned, it seems we have no choice when using Builbot
we now get this issue:
        Caused by: org.jruby.exceptions.LoadError: (LoadError) no such file to load -- asciidoctor-pdf
        at org.jruby.RubyKernel.require(org/jruby/RubyKernel.java:1017)
        at RUBY.require(uri:classloader:/META-INF/jruby.home/lib/ruby/stdlib/rubygems/core_ext/kernel_require.rb:85)
        at RUBY.<main>(<script>:1)
So we only generate HTML5.

I guess I'll need to do the same for all AsciidoctorTaskS...

Author: JacquesLeRoux

build.gradle

@@ -558,12 +558,18 @@ tasks.withType(AsciidoctorTask) { task ->
             jvmArgs("--add-opens","java.base/sun.nio.ch=ALL-UNNAMED","--add-opens","java.base/java.io=ALL-UNNAMED")
         }
     outputOptions {
-         // I hate we have to do this - but JRuby (asciidoctorj-pdf) and Windows don't mix well
-        if (System.properties['os.name'].toLowerCase().contains('windows')) {
-            backends = ['html5']
-        } else {
-            backends = ['html5', 'pdf']
-        }
+//         // I hate we have to do this - but JRuby (asciidoctorj-pdf) and Windows don't mix well
+//        if (System.properties['os.name'].toLowerCase().contains('windows')) {
+//            backends = ['html5']
+//        } else {
+//            backends = ['html5', 'pdf']
+//        }
+         //It seems we have no choice when using Builbot we get this issue:
+//        Caused by: org.jruby.exceptions.LoadError: (LoadError) no such file to load -- asciidoctor-pdf
+//        at org.jruby.RubyKernel.require(org/jruby/RubyKernel.java:1017)
+//        at RUBY.require(uri:classloader:/META-INF/jruby.home/lib/ruby/stdlib/rubygems/core_ext/kernel_require.rb:85)
+//        at RUBY.<main>(<script>:1)
+//        backends = ['html5']
     }
     attributes \
         'doctype': 'book',