Merge pull request libgit2#5700 from libgit2/ethomson/arm-actions

ci: GitHub Actions for arm64

Author: ethomson

.github/workflows/nightly.yml

@@ -2,6 +2,7 @@
 name: Nightly Build
 
 on:
+  workflow_dispatch:
   schedule:
   - cron: '15 1 * * *'
 
@@ -65,6 +66,10 @@ jobs:
             SKIP_NEGOTIATE_TESTS: true
             ASAN_SYMBOLIZER_PATH: /usr/bin/llvm-symbolizer-10
           os: ubuntu-latest
+        - # linux arm64
+          os: [ linux, arm64, self-hosted ]
+          env:
+            CMAKE_OPTIONS: -DDEPRECATE_HARD=ON -DUSE_LEAK_CHECKER=valgrind -DUSE_GSSAPI=ON
         - # macOS
           os: macos-10.15
           env: