Break out Linux bootstrap into its own environment

We want to do bootstrap in a completely Pony free environment. Previously,
it was being done in an environment that had Pony installed. It probably
wouldn't ever be a problem, but this is a better test setup.

.ci-dockerfiles/alpine-bootstrap-tester/Dockerfile

@@ -0,0 +1,10 @@
+FROM alpine:3.11
+
+RUN apk update \
+  && apk upgrade \
+  && apk add --update \
+     build-base \
+     curl \
+     git \
+     libressl-dev \
+     make

.ci-dockerfiles/alpine-bootstrap-tester/build-and-push.bash

@@ -0,0 +1,15 @@
+#!/bin/bash
+
+set -o errexit
+set -o nounset
+
+#
+# *** You should already be logged in to DockerHub when you run this ***
+#
+
+TODAY=$(date +%Y%m%d)
+DOCKERFILE_DIR="$(dirname "$0")"
+
+docker build --pull -t "ponylang/ponyup-ci-alpine-bootstrap-tester:${TODAY}" \
+  "${DOCKERFILE_DIR}"
+docker push "ponylang/ponyup-ci-alpine-bootstrap-tester:${TODAY}"

.ci-dockerfiles/ubuntu-bootstrap-tester/Dockerfile

@@ -0,0 +1,10 @@
+FROM ubuntu:18.04
+
+RUN apt-get update \
+  && apt-get upgrade \
+  && apt-get install -y \
+     gcc \
+     curl \
+     git \
+     libssl-dev \
+     make

.ci-dockerfiles/ubuntu-bootstrap-tester/build-and-push.bash

@@ -0,0 +1,15 @@
+#!/bin/bash
+
+set -o errexit
+set -o nounset
+
+#
+# *** You should already be logged in to DockerHub when you run this ***
+#
+
+TODAY=$(date +%Y%m%d)
+DOCKERFILE_DIR="$(dirname "$0")"
+
+docker build --pull -t "ponylang/ponyup-ci-ubuntu-bootstrap-tester:${TODAY}" \
+  "${DOCKERFILE_DIR}"
+docker push "ponylang/ponyup-ci-ubuntu-bootstrap-tester:${TODAY}"

.ci-scripts/test-bootstrap.sh

@@ -1,13 +1,6 @@
 #!/bin/sh
 
-rm -rf \
-  /usr/local/bin/ponyc \
-  /usr/local/bin/stable \
-  /usr/local/lib/x86-64/libpony* \
-  /usr/local/include/pony* \
-  /usr/local/packages
-
-cat ponyup-init.sh | sh -s -- --prefix=/usr/local
+cat ponyup-init.sh | sh -s
 
 export PATH=$HOME/.local/share/ponyup/bin:$PATH
 ponyup update ponyc nightly "--platform=$(cc -dumpmachine)"

.github/workflows/pr.yml

@@ -40,9 +40,29 @@ jobs:
       - uses: actions/checkout@v1
       - name: Test with the most recent ponyc release
         run: make test
+
+  alpine-bootstrap:
+    name: Test bootstrapping on Alpine
+    runs-on: ubuntu-latest
+    container:
+        image: ponylang/ponyup-ci-alpine-bootstrap-tester:20191228
+    steps:
+      - uses: actions/checkout@v1
       - name: Bootstrap test
         run: .ci-scripts/test-bootstrap.sh
 
+  ubuntu-bootstrap:
+    name: Test bootstrapping on Ubuntu
+    runs-on: ubuntu-latest
+    container:
+        image: ponylang/ponyup-ci-ubuntu-bootstrap-tester:20191228
+    steps:
+      - uses: actions/checkout@v1
+      - name: Bootstrap test
+        run: |
+          export ssl=1.1.x
+          .ci-scripts/test-bootstrap.sh
+
   macos:
     name: Verify PR builds on macOS with most recent ponyc release
     runs-on: macos-latest