Support YACC environment variable for ripper.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@67149 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ext/ripper/depend

@@ -1,7 +1,6 @@
 GEN  = $(srcdir)/tools/generate.rb
 SRC1 = $(top_srcdir)/parse.y
 SRC2 = $(srcdir)/eventids2.c
-BISON = bison
 
 .SUFFIXES: .y
 

ext/ripper/extconf.rb

@@ -5,7 +5,7 @@ require 'mkmf'
 require 'rbconfig'
 
 def main
-  unless find_executable('bison')
+  unless find_executable(ENV["YACC"] || 'bison')
     unless File.exist?('ripper.c') or File.exist?("#{$srcdir}/ripper.c")
       raise 'missing bison; abort'
     end
@@ -16,7 +16,9 @@ def main
   $defs << '-DRIPPER_DEBUG' if $debug
   $VPATH << '$(topdir)' << '$(top_srcdir)'
   $INCFLAGS << ' -I$(topdir) -I$(top_srcdir)'
-  create_makefile 'ripper'
+  create_makefile 'ripper' do |conf|
+    conf << "BISON = #{ENV['YACC'] || 'bison'}"
+  end
 end
 
 main