libsvm.pc has been dropped in the 2.90-1 upload of libsvm.  Set the
necessary CFLAGS and LDFLAGS manually in extconf.rb.  Closes #560541.

Index: libsvm-ruby-2.8.5/extconf.rb
===================================================================
--- libsvm-ruby-2.8.5.orig/extconf.rb	2009-12-15 19:13:06.000000000 +0100
+++ libsvm-ruby-2.8.5/extconf.rb	2009-12-15 19:13:50.000000000 +0100
@@ -1,8 +1,8 @@
 require 'mkmf'
 #have_library('stdc++', "main")
 #have_library('svm', "main")
-$CFLAGS = "#{ENV['CFLAGS']} -Wall -O3 "
-pkg_config 'libsvm'
+$CFLAGS = "#{ENV['CFLAGS']} -Wall -O3 -I/usr/include/libsvm-2.0/libsvm "
+$LDFLAGS = "#{ENV['LDFLAGS']} -lsvm "
 if CONFIG["MAJOR"].to_i >= 1 && CONFIG["MINOR"].to_i >= 8
   $CFLAGS << " -DHAVE_DEFINE_ALLOC_FUNCTION"
 end