ci: serialize make distcheck in build.yml

The parallel distcheck is full of potentiall race conditions because
there is no defined ordering on the libraries. There were attempts to
fix this using CI, but fixed one problem just revealed another one and
ultimately the fix was becomming more complex and magical but still
incomplete.

Reviewed-by: Alexey Tikhonov <atikhono@redhat.com>
(cherry picked from commit df13bd9)

Author: pbrezina

.github/workflows/build.yml

@@ -45,7 +45,9 @@ jobs:
       working-directory: x86_64
       run: |
         source ../contrib/fedora/bashrc_sssd
-        make -j$PROCESSORS distcheck
+
+        # parallel distcheck is full of race conditions
+        make -j1 distcheck
 
     - uses: actions/upload-artifact@v7
       if: always()