move linux builds to buildkite (#67)

.buildkite/pipeline.yml

@@ -0,0 +1,4 @@
+steps:
+  - group: Build
+    steps:
+    - command: zig build -Drelease-small

.github/workflows/build.yml

@@ -5,7 +5,7 @@ on:
   pull_request:
     branches: [ master ]
   schedule:
-    - cron: "0 7 * * *"
+    - cron: "0 0 * * *"
 
 jobs:
   build:
@@ -13,7 +13,6 @@ jobs:
     strategy:
       matrix:
         os: [
-          ubuntu-latest,
           windows-latest,
           macos-latest,
         ]
@@ -24,7 +23,6 @@ jobs:
         submodules: recursive
         fetch-depth: 0
 
-    # only using master until 0.9.0 is released
     - name: Setup Zig
       uses: goto-bus-stop/setup-zig@v1.3.0
       with: