[github actions] Fix workflow
diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 2ef481f..c11d391 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -4,7 +4,10 @@
 
 jobs:
   build:
-    runs-on: [ubuntu-latest, macos-latest]
+    strategy:
+      matrix:
+        platform: [ubuntu-latest, macos-latest]
+    runs-on: ${{ matrix.platform }}
     steps:
     - uses: actions/checkout@v1
     - name: autogen