Recommend building with -disable-job-server

Until and if we implement a job server scheme for Fuchsia,
we should disable it so we can build with -j, even if there
is no global load balancing.

Change-Id: Iad558e9b5b0850b2d00a6017072586d94016d3c0

README.md

diff --git a/README.md b/README.md
index 9a790c9..faca6fd 100644
--- a/README.md
+++ b/README.md
@@ -9,6 +9,7 @@
 ```
   $ <path-to-make>/configure \
           --host=<arch>-fuchsia \
+          --disable-job-server \
           CC=<path-to-compiler>/<arch>-fuchsia-gcc
 ```
   (where `<arch>` is one of: `x86_64`, `aarch64`, or `arm`)