[ruby/rubygems] Take one timestamp per multi-source repo build

Stamping each solo_gem with its own Time.now.utc lets the two dates
drift apart and matches neither the surrounding before block. Snapshot
the time once so the cooldown window stays stable as thresholds tighten.

ruby/rubygems@69c6d876d4

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: 2 people

spec/bundler/install/cooldown_spec.rb

@@ -489,12 +489,13 @@
     end
 
     it "keeps a top-level source cooldown through a partial update with multiple sources" do
+      now = Time.now.utc
       build_repo4 do
         build_gem "solo_gem", "1.0.0" do |s|
-          s.date = Time.now.utc - (30 * 86_400)
+          s.date = now - (30 * 86_400)
         end
         build_gem "solo_gem", "2.0.0" do |s|
-          s.date = Time.now.utc - (1 * 86_400)
+          s.date = now - (1 * 86_400)
         end
       end
 
@@ -537,12 +538,13 @@
     end
 
     it "carries cooldown declared on a gem-block source" do
+      now = Time.now.utc
       build_repo4 do
         build_gem "solo_gem", "1.0.0" do |s|
-          s.date = Time.now.utc - (30 * 86_400)
+          s.date = now - (30 * 86_400)
         end
         build_gem "solo_gem", "2.0.0" do |s|
-          s.date = Time.now.utc - (1 * 86_400)
+          s.date = now - (1 * 86_400)
         end
       end