Add test_alpine to circleci config

.circleci/config.yml

@@ -39,6 +39,16 @@ jobs:
       ARCH_CMD: linux32
     steps: *ci_steps
 
+  test_alpine:
+    docker:
+    - image: jrei/crystal-alpine:latest
+    environment:
+      <<: *env
+      TRAVIS_OS_NAME: linux
+      ARCH: x86_64
+      ARCH_CMD: linux64
+    steps: *ci_steps
+
   test_darwin:
     macos:
       xcode: "9.0"
@@ -343,6 +353,8 @@ workflows:
                 - /.*\bci\b.*/
       - test_linux32:
           filters: *unless_maintenance
+      - test_alpine:
+          filters: *unless_maintenance
       - test_darwin:
           filters: *unless_maintenance
       - check_format:
@@ -365,6 +377,8 @@ workflows:
               only: /.*/
       - test_linux32:
           filters: *per_tag
+      - test_alpine:
+          filters: *per_tag
       - test_darwin:
           filters: *per_tag
       - check_format:
@@ -426,6 +440,7 @@ workflows:
     jobs:
       - test_linux
       - test_linux32
+      - test_alpine
       - test_darwin
       - check_format
       - prepare_common:
@@ -476,6 +491,8 @@ workflows:
                 - /.*\bci\b.*/
       - test_linux32:
           filters: *maintenance
+      - test_alpine:
+          filters: *maintenance
       - test_darwin:
           filters: *maintenance
       - check_format: