Faster builds by limiting visible CPUs

As described in this elm compiler issue:
elm/compiler#1473

.travis.yml

@@ -15,6 +15,7 @@ before_install:
 
 install:
   - ./install_protobuf
+  - ./install_sysconfcpus
   - export PATH=$PATH:$PWD/protoc/bin
   - go get -t -v ./protoc-gen-elm
   - protoc --version

install_sysconfcpus

@@ -0,0 +1,10 @@
+#!/bin/bash
+
+set -ex
+
+echo "Install libsysconfcpus to compensate for slow elm builds"
+# More at: https://github.com/elm/compiler/issues/1473
+git clone https://github.com/obmarg/libsysconfcpus.git
+cd libsysconfcpus
+./configure && make && sudo make install
+cd ..

protoc-gen-elm/elm_tests/run_elm_tests

@@ -11,5 +11,11 @@ readonly ROOT="$(dirname "$0")"
 
 (
   cd ${ROOT}
-  elm-test
+  # If sysconfcpus is on path, as on travis, then limit the number of
+  # visible CPUs to 1 to work around the elm problems with many CPUs.
+  if [ -x "$(command -v sysconfcpus)" ]; then
+      sysconfcpus -n 1 elm-test
+  else
+      elm-test
+  fi
 )