Fix Java API reference build

Java 11 JavaDoc requires error free source files (html tags, imports,
etc) in order to produce the API reference. Use "--ignore-source-errors"
parameter to fall back to Java 8 JavaDoc behavior.

Bug 579677: Broken JavaDocs links in online developer's guide
https://bugs.eclipse.org/bugs/show_bug.cgi?id=579677

Change-Id: I38197af32b3fe2828df88302149c5761a5315d93
diff --git a/bundles/org.eclipse.rap.doc/reference-build/build.xml b/bundles/org.eclipse.rap.doc/reference-build/build.xml
index ffc202b..cbea0a5 100755
--- a/bundles/org.eclipse.rap.doc/reference-build/build.xml
+++ b/bundles/org.eclipse.rap.doc/reference-build/build.xml
@@ -19,6 +19,7 @@
         version="true"
         use="true"
         useexternalfile="yes"
+        additionalparam="--ignore-source-errors"
         windowtitle="Eclipse RAP ${version} API Reference"
         packagenames="org.eclipse.rap.rwt.*"
         excludePackageNames="org.eclipse.rap.rwt.internal.*,org.eclipse.swt.internal.*">