doc: Build documentation in parallel

With the addition of the revision stats this now takes over a minute. Use
a parallel build to reduce it a bit (24 seconds for me).

Series-changes; 2
- Use '-j auto' instead

Signed-off-by: Simon Glass <sjg@chromium.org>

diff --git a/doc/Makefile b/doc/Makefile
index 6081858..f5de65e 100644 (file)
--- a/doc/Makefile
+++ b/doc/Makefile
@@ -58,6 +58,7 @@ quiet_cmd_sphinx = SPHINX  $@ --> file://$(abspath $(BUILDDIR)/$3/$4)
        $(SPHINXBUILD) \
        -j$(shell nproc) \
        -b $2 \
+       -j auto \
        -c $(abspath $(srctree)/$(src)) \
        -d $(abspath $(BUILDDIR)/.doctrees/$3) \
        -D version=$(KERNELVERSION) -D release=$(KERNELRELEASE) \