[ruby/tempfile] Fix subprocess tests requires

Using `-rtempfile` requires the tempfile built into Ruby, not the
currently developed one, so the tests aren't testing this tempfile.

https://github.com/ruby/tempfile/commit/ea2dec6f46

test/test_tempfile.rb

@@ -175,7 +175,7 @@ class TestTempfile < Test::Unit::TestCase
   end unless /mswin|mingw/ =~ RUBY_PLATFORM
 
   def test_finalizer_removes_file
-    assert_in_out_err(["-r#{LIB_TEMPFILE_RB_PATH}"], <<~RUBY) do |(filename,*), (error,*)|
+    assert_in_out_err("-r#{LIB_TEMPFILE_RB_PATH}", <<~RUBY) do |(filename,*), (error,*)|
       file = Tempfile.new("foo")
       puts file.path
     RUBY
@@ -185,7 +185,7 @@ class TestTempfile < Test::Unit::TestCase
   end
 
   def test_finalizer_removes_file_when_dup
-    assert_in_out_err(["-r#{LIB_TEMPFILE_RB_PATH}"], <<~RUBY) do |(filename,*), (error,*)|
+    assert_in_out_err("-r#{LIB_TEMPFILE_RB_PATH}", <<~RUBY) do |(filename,*), (error,*)|
       file = Tempfile.new("foo")
       file.dup
       puts file.path
@@ -196,7 +196,7 @@ class TestTempfile < Test::Unit::TestCase
   end
 
   def test_finalizer_removes_file_when_clone
-    assert_in_out_err(["-r#{LIB_TEMPFILE_RB_PATH}"], <<~RUBY) do |(filename,*), (error,*)|
+    assert_in_out_err("-r#{LIB_TEMPFILE_RB_PATH}", <<~RUBY) do |(filename,*), (error,*)|
       file = Tempfile.new("foo")
       file.clone
       puts file.path
@@ -207,7 +207,7 @@ class TestTempfile < Test::Unit::TestCase
   end
 
   def test_finalizer_does_not_unlink_if_already_unlinked
-    assert_in_out_err('-rtempfile', <<-'EOS') do |(filename,*), (error,*)|
+    assert_in_out_err("-r#{LIB_TEMPFILE_RB_PATH}", <<-'EOS') do |(filename,*), (error,*)|
 file = Tempfile.new('foo')
 path = file.path
 puts path
@@ -219,7 +219,7 @@ File.open(path, "w").close
       assert_nil error
     end
 
-    assert_in_out_err('-rtempfile', <<-'EOS') do |(filename,*), (error,*)|
+    assert_in_out_err("-r#{LIB_TEMPFILE_RB_PATH}", <<-'EOS') do |(filename,*), (error,*)|
 file = Tempfile.new('foo')
 path = file.path
 file.unlink
@@ -249,7 +249,7 @@ File.open(path, "w").close
   end
 
   def test_tempfile_is_unlinked_when_ruby_exits
-    assert_in_out_err('-rtempfile', <<-'EOS') do |(filename), (error)|
+    assert_in_out_err("-r#{LIB_TEMPFILE_RB_PATH}", <<-'EOS') do |(filename), (error)|
 puts Tempfile.new('foo').path
     EOS
       assert_file.for("tempfile must not be exist after GC.").not_exist?(filename)
@@ -259,7 +259,7 @@ puts Tempfile.new('foo').path
 
   def test_tempfile_finalizer_does_not_run_if_unlinked
     bug8768 = '[ruby-core:56521] [Bug #8768]'
-    assert_in_out_err(%w(-rtempfile), <<-'EOS') do |(filename), (error)|
+    assert_in_out_err("-r#{LIB_TEMPFILE_RB_PATH}", <<-'EOS') do |(filename), (error)|
       tmp = Tempfile.new('foo')
       puts tmp.path
       tmp.close