Force use of UTC in formatting seconds into MM:SS

The job trace logs section parser computes section
durations for the UIs by computing differences in
epoch timestamps between the sections.

However, when building the string represntation of
the duration in MM:SS, its reliance on the Time
library and the epoch time
(0 seconds -> 00:00, extracted from 1970-01-01 00:00:00)
means that it can be influenced by the timezone of the
install host.

When timezone of the host uses non-UTC types and involves
an offset, such as +0530 (India Standard Time) then the
UI displayed section durations of 00:NN as 30:NN.

This change forces a UTC conversion of the computed
epoch time from the seconds, which should help with
showing the right duration values regardless of local
timezone.

Closes issue: https://gitlab.com/gitlab-org/gitlab/-/issues/332296

Changelog: fixed

lib/gitlab/ci/ansi2json/line.rb

@@ -77,7 +77,7 @@ module Gitlab
         end
 
         def set_section_duration(duration)
-          @section_duration = Time.at(duration.to_i).strftime('%M:%S')
+          @section_duration = Time.at(duration.to_i).utc.strftime('%M:%S')
         end
 
         def flush_current_segment!

spec/lib/gitlab/ci/ansi2json/line_spec.rb

@@ -76,10 +76,25 @@ RSpec.describe Gitlab::Ci::Ansi2json::Line do
   end
 
   describe '#set_section_duration' do
-    it 'sets and formats the section_duration' do
-      subject.set_section_duration(75)
 
-      expect(subject.section_duration).to eq('01:15')
+    shared_examples 'set_section_duration' do
+      it 'sets and formats the section_duration' do
+        subject.set_section_duration(75)
+
+        expect(subject.section_duration).to eq('01:15')
+      end
+    end
+
+    context 'with default timezone' do
+      it_behaves_like 'set_section_duration'
+    end
+
+    context 'with a timezone carrying minutes offset' do
+      before do
+        allow(Time).to receive(:at).with(75).and_return(Time.at(75, in: '+05:30'))
+      end
+
+      it_behaves_like 'set_section_duration'
     end
   end