fix test_readline#test_without_tty failure

ruby/ruby#5417

Author: sorah

debian/patches/series

@@ -6,3 +6,4 @@ exclude-several-tests-unstable-in-Docker.patch
 Fix-FTBFS-on-x32-misdetected-as-i386-or-amd64.patch
 TestProcess-disable-gems-to-disable-rubygems_integration.patch
 ruby_default_arch.m4-don-t-require-arhitectures-to-be-kno.patch
+test_readline-test_without_tty-Use-EnvUtil.rubybin.patch

debian/patches/test_readline-test_without_tty-Use-EnvUtil.rubybin.patch

@@ -0,0 +1,32 @@
+From: Sorah Fukumori <[email protected]>
+Date: Sat, 8 Jan 2022 14:03:02 +0900
+Subject: test_readline#test_without_tty: Use EnvUtil.rubybin
+
+`ruby` is not always available in certain build environments and
+configure options. Choose appropriate command line using EnvUtil.
+---
+ test/readline/test_readline.rb | 4 +++-
+ 1 file changed, 3 insertions(+), 1 deletion(-)
+
+diff --git a/test/readline/test_readline.rb b/test/readline/test_readline.rb
+index be338c6..be6e65f 100644
+--- a/test/readline/test_readline.rb
++++ b/test/readline/test_readline.rb
+@@ -6,6 +6,8 @@ require "timeout"
+ require "open3"
+ 
+ module BasetestReadline
++  RUBY = EnvUtil.rubybin
++
+   INPUTRC = "INPUTRC"
+   TERM = "TERM"
+   SAVED_ENV = %w[COLUMNS LINES]
+@@ -839,7 +841,7 @@ module BasetestReadline
+       loader = "use_lib_reline"
+     end
+     if loader
+-      res, exit_status = Open3.capture2e("ruby -I#{__dir__} -Ilib -rhelper -e '#{loader}; Readline.readline(%{y or n?})'", stdin_data: "y\n")
++      res, exit_status = Open3.capture2e("#{RUBY} -I#{__dir__} -Ilib -rhelper -e '#{loader}; Readline.readline(%{y or n?})'", stdin_data: "y\n")
+       assert exit_status.success?, "It should work fine without tty, but it failed.\nError output:\n#{res}"
+     end
+   end