CI: ubuntu-ibm.yml: Set the runner user's primary group from the "id -g".

Set the runner user's primary group to avoid a mismatch between the group IDs of
"id -g" and C function getpwuid(uid_t uid) pw_gid in a test as a better
workaround.

Author: junaruga

.github/workflows/ubuntu-ibm.yml

@@ -134,15 +134,12 @@ jobs:
         continue-on-error: true
         timeout-minutes: 3
 
-      # A temporary workaround: Skip user ground id test
-      # There is a mismatch between the group IDs of "id -g" and C function
-      # getpwuid(uid_t uid) pw_gid.
+      # A temporary workaround: Set the user's primary group to avoid a mismatch
+      # between the group IDs of "id -g" and C function getpwuid(uid_t uid)
+      # pw_gid.
       # https://github.com/IBM/actionspz/issues/31
-      - name: Skip user group id test
-        run: |
-          sed -i.orig '/^    it "returns user group id" do/a\      skip' \
-            ../src/spec/ruby/library/etc/struct_passwd_spec.rb
-          diff -u ../src/spec/ruby/library/etc/struct_passwd_spec.rb{.orig,} || :
+      - name: Set user's group id
+        run: sudo usermod -g "$(id -g)" runner
         if: ${{ endsWith(matrix.os, 'ppc64le') || endsWith(matrix.os, 's390x') }}
 
       - name: make ${{ matrix.test_task }}