Remove osx support.

.travis.yml

@@ -73,13 +73,13 @@ jobs:
   #   addons: {apt: {packages: [libgmp-dev]}}
 
   # Nightly builds are allowed to fail
-  - env: BUILD=stack ARGS="--resolver nightly"
+  - env: BUILD=stack ARGS="--stack-yaml stack_nightly.yaml"
     compiler: ": #stack nightly"
     addons: {apt: {packages: [libgmp-dev]}}
 
   allow_failures:
   - env: BUILD=cabal GHCVER=head  CABALVER=head HAPPYVER=1.19.5 ALEXVER=3.1.7
-  - env: BUILD=stack ARGS="--resolver nightly"
+  - env: BUILD=stack ARGS="--stack-yaml stack_nightly.yaml"
 
 before_install:
 # Using compiler above sets CC to an invalid value, so unset it
@@ -93,12 +93,7 @@ before_install:
 - export PATH=/opt/ghc/$GHCVER/bin:/opt/cabal/$CABALVER/bin:$HOME/.local/bin:/opt/alex/$ALEXVER/bin:/opt/happy/$HAPPYVER/bin:$HOME/.cabal/bin:$PATH
 - mkdir -p ~/.local/bin
 - |
-  if [ `uname` = "Darwin" ]
-  then
-    travis_retry curl --insecure -L https://get.haskellstack.org/stable/osx-x86_64.tar.gz | tar xz --strip-components=1 --include '*/stack' -C ~/.local/bin
-  else
-    travis_retry curl -L https://get.haskellstack.org/stable/linux-x86_64.tar.gz | tar xz --wildcards --strip-components=1 -C ~/.local/bin '*/stack'
-  fi
+  travis_retry curl -L https://get.haskellstack.org/stable/linux-x86_64.tar.gz | tar xz --wildcards --strip-components=1 -C ~/.local/bin '*/stack'
 
   # Use the more reliable S3 mirror of Hackage
   mkdir -p $HOME/.cabal

stack_nightly.yaml

@@ -0,0 +1,6 @@
+flags:
+  keter: {}
+packages:
+- '.'
+extra-deps: []
+resolver: nightly-2020-02-20