Fixes in Dockerfiles for Node, PHP, Ruby, speed boost for Python
diff --git a/tools/dockerfile/grpc_python/Dockerfile b/tools/dockerfile/grpc_python/Dockerfile
index 362227b..901375c 100644
--- a/tools/dockerfile/grpc_python/Dockerfile
+++ b/tools/dockerfile/grpc_python/Dockerfile
@@ -1,13 +1,13 @@
# Dockerfile for GRPC Python
FROM grpc/python_base
-# Build the C library
+# Pull the latest sources
RUN cd /var/local/git/grpc \
&& git pull --recurse-submodules \
&& git submodule update --init --recursive
# Build the C core.
-RUN make install_c -C /var/local/git/grpc
+RUN make install_c -j12 -C /var/local/git/grpc
# Build Python GRPC
RUN cd /var/local/git/grpc \