Previously for every html rendered, there's a separate jvm used, and buck's
parallel building will execute multiple jvm at once, burning the CPU and being
very slow.
Modified the asciidoctor-java-integrator CLI java wrapper interface to do that
all in a single jvm.
On a workstation tested, "buck build Documentation:html" took about 140s before,
and 60s after.
As a side-effect, we lose the build rules of the single html files (e.g.
"buck build Documentation:licenses.html")
Change-Id: Ifc70c63676b59571c6e240636752b7cba9270f04
29db1f67b3