ci: add OS matrix for build jobs in workflows

Author: AhmedSobhy01

.github/workflows/build.yml

@@ -27,6 +27,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
+        os: [ubuntu-latest, windows-latest]
         include:
           - name: Ubuntu / GCC
             os: ubuntu-latest

.github/workflows/release.yml

@@ -35,6 +35,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
+        os: [ubuntu-latest, windows-latest]
         include:
           - name: Linux
             os: ubuntu-latest