[rubygems/rubygems] Make the test suite pass under umask 077

Some tests had failed under `umask 077` mode.  As far as I investigated,
there is no actual bug.  All failures were caused by tests that create a
wrong-permission file or expect wrong permission.

This changeset fixes the tests.

078213e527

test/rubygems/test_gem_commands_build_command.rb

@@ -17,9 +17,14 @@ class TestGemCommandsBuildCommand < Gem::TestCase
 
     readme_file = File.join(@tempdir, 'README.md')
 
+    begin
+      umask_orig = File.umask(2)
       File.open readme_file, 'w' do |f|
         f.write 'My awesome gem'
       end
+    ensure
+      File.umask(umask_orig)
+    end
 
     @gem = util_spec 'some_gem' do |s|
       s.license = 'AGPL-3.0'

test/rubygems/test_gem_installer.rb

@@ -2200,7 +2200,7 @@ gem 'other', version
   end
 
   def mask
-    0100755 & (~File.umask)
+    0100755
   end
 
 end

test/rubygems/test_gem_specification.rb

@@ -3823,6 +3823,8 @@ end
       FileUtils.mkdir_p "test"
       FileUtils.mkdir_p "bin"
 
+      begin
+        umask_orig = File.umask(2)
         FileUtils.touch File.join("ext", "a", "extconf.rb")
         FileUtils.touch File.join("lib", "code.rb")
         FileUtils.touch File.join("test", "suite.rb")
@@ -3830,6 +3832,9 @@ end
         File.open "bin/exec", "w", 0755 do |fp|
           fp.puts "#!#{Gem.ruby}"
         end
+      ensure
+        File.umask(umask_orig)
+      end
     end
   end