sage_setup.docbuild.AllBuilder: stop the non-reference manual docs fr…

…om being built in parallel

src/sage_setup/docbuild/__init__.py

@@ -286,13 +286,15 @@ def clean(self, *args):
 
 from .utils import build_many as _build_many
 
-def build_many(target, args):
+def build_many(target, args, processes=None):
     """
     Thin wrapper around `sage_setup.docbuild.utils.build_many` which uses the
     docbuild settings ``NUM_THREADS`` and ``ABORT_ON_ERROR``.
     """
+    if processes is None:
+        processes = NUM_THREADS
     try:
-        _build_many(target, args, processes=NUM_THREADS)
+        _build_many(target, args, processes=processes)
     except BaseException as exc:
         if ABORT_ON_ERROR:
             raise
@@ -349,7 +351,7 @@ def _wrapper(self, name, *args, **kwds):
 
         # build the other documents in parallel
         L = [(doc, name, kwds) + args for doc in others]
-        build_many(build_other_doc, L)
+        build_many(build_other_doc, L, 1)
         logger.warning("Elapsed time: %.1f seconds."%(time.time()-start))
         logger.warning("Done building the documentation!")