Run ARM-specific tests consistently (#434)

* Run ARM-specific test consistently

* Fix for builds.hex.pm

https://builds.hex.pm/builds/otp/arm64/ubuntu-<x>.04/builds.txt

file is only available when <x> >= 20.

* Fix for builds.hex.pm

https://builds.hex.pm/builds/otp/arm64/ubuntu-20.04/builds.txt

does not contain Erlang 19 any more...

.github/workflows/action.yml

@@ -63,7 +63,12 @@ jobs:
 
   unit_tests_ubuntu:
     name: Unit tests (Ubuntu)
-    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        os:
+          - ubuntu-24.04-arm # ARM64
+          - ubuntu-latest # x86_64
+    runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/checkout@v6.0.2
       - uses: actions/setup-node@v6.3.0
@@ -84,7 +89,12 @@ jobs:
 
   unit_tests_windows:
     name: Unit tests (Windows)
-    runs-on: windows-latest
+    strategy:
+      matrix:
+        os:
+          - windows-11-arm # ARM64
+          - windows-latest # x86_64
+    runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/checkout@v6.0.2
       - uses: actions/setup-node@v6.3.0
@@ -105,7 +115,12 @@ jobs:
 
   unit_tests_macos:
     name: Unit tests (macOS)
-    runs-on: macos-latest
+    strategy:
+      matrix:
+        os:
+          - macos-latest # ARM64
+          - macos-15-intel # x86_64
+    runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/checkout@v6.0.2
       - uses: actions/setup-node@v6.3.0