add RUNRUBY_USE_GDB envvar for runruby.rb.

* tool/runruby.rb: add RUNRUBY_USE_GDB environment variable.
  If RUNRUBY_USE_GDB=true then use 'gdb --args'.
  If there is 'run.gdb' file (made by 'make run.gdb') on current directory,
  run gdb with this file ('gdb -x run.gdb --args').

  This envval is useful when you want to run test-all (and so on) with gdb.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@60245 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

tool/runruby.rb

@@ -106,6 +106,14 @@ end
 
 ENV.update env
 
+if ENV['RUNRUBY_USE_GDB'] == 'true'
+  if File.exist?('run.gdb')
+    precommand = %w'gdb -x run.gdb --args'
+  else
+    precommand = %w'gdb --args'
+  end
+end
+
 cmd = [runner || ruby]
 cmd.concat(ARGV)
 cmd.unshift(*precommand) unless precommand.empty?