Fix YAML indentation and use python instead of python3

.github/workflows/build.yml

@@ -45,17 +45,17 @@ jobs:
 
     - name: Generate package list
       run: |
-        python3 -c "
-import json, os, glob
-pkgs = []
-for f in glob.glob('/tmp/pkgout/*.pkg.tar.zst'):
-    name = os.path.basename(f)
-    size = os.path.getsize(f)
-    pkgs.append({'name': name, 'size': size})
-with open('repo/pkglist.json', 'w') as fp:
-    json.dump(pkgs, fp, indent=2)
-    fp.write('\n')
-"
+        python -c "
+        import json, os, glob
+        pkgs = []
+        for f in glob.glob('/tmp/pkgout/*.pkg.tar.zst'):
+            name = os.path.basename(f)
+            size = os.path.getsize(f)
+            pkgs.append({'name': name, 'size': size})
+        with open('repo/pkglist.json', 'w') as fp:
+            json.dump(pkgs, fp, indent=2)
+            fp.write('\n')
+        "
 
     - name: Deploy to Pages
       uses: peaceiris/actions-gh-pages@v3