rake/backtrace.rb: exclude mere prefix

* lib/rake/backtrace.rb (Rake::Backtrace): exclude mere prefix and
  exec_prefix, which match too much.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47200 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/rake/backtrace.rb

@@ -1,6 +1,6 @@
 module Rake
   module Backtrace # :nodoc: all
-    SYS_KEYS  = RbConfig::CONFIG.keys.grep(/(?:prefix|libdir)\z/)
+    SYS_KEYS  = RbConfig::CONFIG.keys.grep(/(?:[a-z]prefix|libdir)\z/)
     SYS_PATHS = RbConfig::CONFIG.values_at(*SYS_KEYS).uniq +
       [ File.join(File.dirname(__FILE__), "..") ]
 

test/rake/test_rake_backtrace.rb

@@ -42,7 +42,7 @@ class TestRakeBacktrace < Rake::TestCase
     super
 
     skip 'tmpdir is suppressed in backtrace' if
-      Dir.pwd =~ Rake::Backtrace::SUPPRESS_PATTERN
+      Rake::Backtrace::SUPPRESS_PATTERN =~ Dir.pwd
   end
 
   def invoke(*args)