Add flang docs to SphinxDocsBuilder.

Since flang Sphinx docs are buildable, we can expand SphinxDocsBuilder to build and publish.

Require
sphinx==1.8.5
sphinx-markdown-tables==0.0.14
recommonmark==0.6.0

Reviewed By: gkistanova

Differential Revision: https://reviews.llvm.org/D91116
diff --git a/zorg/buildbot/builders/SphinxDocsBuilder.py b/zorg/buildbot/builders/SphinxDocsBuilder.py
index f24f07e..a724e46 100644
--- a/zorg/buildbot/builders/SphinxDocsBuilder.py
+++ b/zorg/buildbot/builders/SphinxDocsBuilder.py
@@ -15,6 +15,7 @@
   ("libunwind",         ("docs-libunwind-html",   "projects/libunwind/docs/html/",      "libunwind")),
   ("lld",               ("docs-lld-html",         "tools/lld/docs/html/",               "lld")),
   ("lldb",              ("docs-lldb-html",        "tools/lldb/docs/html/",              "lldb")),
+  ('flang',             ("docs-flang-html",       "tools/flang/docs/html/",             "flang")),
   ("openmp",            ("docs-openmp-html",      "projects/openmp/docs/html/",         "openmp")),
   ("polly",             ("docs-polly-html",       "tools/polly/docs/html/",             "polly")),
 ])
@@ -158,6 +159,7 @@
             "libunwind",
             "lld",
             "lldb",
+            "flang",
             "openmp",
             "polly",
         ]