Feature/add dockerfile for newest LTS builds

Dockerfile

@@ -0,0 +1,30 @@
+# Start from the Lambda Env mirror
+FROM lambci/lambda:provided
+
+# Switch to root, so we can install packages and configure users
+USER root
+
+# Install packages required for building GHC
+RUN yum -y install gcc gmp-devel zlib-devel
+
+# Give users access to /tmp, as stack uses it to build GHC
+RUN chmod a=rwx,o+t /tmp
+
+# Custom stack images require a stack group and stack user in the stack group
+RUN /usr/sbin/groupadd stack
+RUN /usr/sbin/useradd stack -g stack
+
+# Switch to the stack user so we can setup its home directory
+USER stack
+RUN mkdir ~/.stack
+ENV PATH=/usr/sbin:$HOME/.local/bin:$PATH
+RUN mkdir -p ~/.local/bin
+
+# Install stack
+RUN curl -L https://get.haskellstack.org/stable/linux-x86_64.tar.gz | tar xz --wildcards --strip-components=1 -C ~/.local/bin '*/stack'
+
+# Switch back to the root user
+USER root
+
+# Disable the default `lambdci/lambda` entrypoint
+ENTRYPOINT []

README.md

@@ -114,14 +114,17 @@ You'll need to either build on a compatible linux host or inside a compatible do
 Note that current Stack LTS images are _not_ compatible.
 If you see an error message that contains "version 'GLIBC_X.XX' not found" when running (hosted or locally), then your build environment is not compatible.
 
+An example Dockerfile is included in this repo, which can build out later Stack LTS snapshots (also see Troubleshooting Builds for Specific Package).
+Build it with `docker build -t ${BUILD_IMAGE_NAME} ${DOCKER_FILE_ROOT_DIR}`.
+
 Enable stack's docker integration and define an optional image within stack.yaml:
 
 ```yaml
 # file: stack.yaml
 docker:
  enabled: true
  # If omitted, this defaults to fpco/stack-build:lts-${YOUR_LTS_VERSION}
- image: ${BUILD_IMAGE}
+ image: ${BUILD_IMAGE_NAME}
 ```
 
 Don't forget to define your [CloudFormation] stack:
@@ -203,6 +206,22 @@ Note that hal currently only supports [aws-sam-cli] on versions <1.0.
 echo '{ "accountId": "byebye" }' | sam local invoke --region us-east-1
 ```
 
+## Troubleshooting Builds for Specific Package
+
+Some packages require a few additional settings to build without issue, where a Docker based solution is impractical.
+
+### cryptonite 0.27
+
+To get this version to build you'll need to pass the Cabal flag `use_target_attributes` false.
+You can put the following in your `stack.yaml` to do this:
+
+```
+flags:
+ cryptonite:
+ use_target_attributes: false
+```
+
+
 [AWS Lambda]: https://docs.aws.amazon.com/lambda/latest/dg/welcome.html
 [Haskell]: https://www.haskell.org/
 [stack.yaml]: https://docs.haskellstack.org/