First stab at running OSX build.

.travis.yml

@@ -1,9 +1,31 @@
-language: nix
-nix: 2.1.3
+# TODO Only do release builds on the `pull` branch?
 
-os:
-  - linux
-  - osx
+jobs:
+  include:
+# - os: linux
+#   language: nix
+#   nix: 2.1.3
+#   install:
+#     - nix-env -iA cachix -f https://cachix.org/api/v1/install
+
+#   script:
+#     - cachix use urbit2
+#     - ./sh/cachix
+#     - make build-fast
+#     - make release
+#     - sh/ci-tests
+
+  - os: osx
+    language: generic
+    sudo: required
+    script:
+      - ver="$(git rev-parse HEAD)"
+      - if [ -n "${TRAVIS_COMMIT-}" ]; then ver="$TRAVIS_COMMIT"; fi
+      - if [ -n "${TRAVIS_TAG-}" ]; then ver="$TRAVIS_TAG"; fi
+      - stack clean
+      - stack install king --local-bin-path ./release
+      - mv release/king release/king-darwin-$ver
+      - otool -L release/king-darwin-$ver
 
 cache:
   directories:
@@ -17,17 +39,8 @@ before_install:
   - sh/travis-install-stack
 
 install:
-  - nix-env -iA cachix -f https://cachix.org/api/v1/install
   - stack --no-terminal --install-ghc build king --only-dependencies
 
-# TODO Only do release builds on the `pull` branch?
-script:
-  - cachix use urbit2
-  - ./sh/cachix || true
-  - make build-fast
-  - make release
-  - sh/ci-tests
-
 deploy:
   - skip_cleanup: true
     provider: gcs

sh/travis-install-stack

@@ -2,20 +2,39 @@
 
 set -ex
 
+
+##
+##  Make sure this is running OSX/Linux in Travis
+##
+
+os="$TRAVIS_OS_NAME"
+
+[ "$os" = osx ] || [ "$os" = linux ]
+
+
+##
+##  Download the stack executable.
+##
+
 mkdir -p ~/.local/bin
 
-# OSX
-# curl -L https://get.haskellstack.org/stable/osx-x86_64.tar.gz | tar xz --strip-components=1 --include '*/stack' -C ~/.local/bin
+stackurl="https://get.haskellstack.org/stable/$os-x86_64.tar.gz"
 
-mkdir -p tmp
+case $os in
+    osx)
+        curl -L "$stackurl" |
+            tar xz --strip-components=1 --include '*/stack' -C ~/.local/bin
+    linux)
+        mkdir -p tmp
+        curl -L "$stackurl" | tar xz -C tmp
+        mv tmp/stack-*/stack ~/.local/bin
+esac
 
-pax="https://get.haskellstack.org/stable/linux-x86_64.tar.gz"
 
-curl -L $pax | tar xz -C tmp
+##
+##  Use the more reliable S3 mirror of Hackage.
+##
 
-mv tmp/stack-*/stack ~/.local/bin
-
-# Use the more reliable S3 mirror of Hackage
 mkdir -p ~/.cabal
 
 cat > ~/.cabal/config <<EOF