Since upgrading to JRuby 1.5 building JRuby from sources fails on one internal QE machine with the following backtrace:

[...]
    [echo] Running rake install_dist_gems
    [echo] compile=OFF, threshold=20, objectspace=true threadpool=false reflection=false
    [java] (in C:/space/hudson/workspace/JMX-Tests/jdk/jdk1.6/label/WinXP-1-stable/o.jruby.distro/unpatched_source/jruby-1.5.0)
    [java] install_dist_gems build_lib/columnize-0.3.1.gem build_lib/rake-0.8.7.gem build_lib/rspec-1.3.0.gem  build_lib/ruby-debug-base-0.10.3.2-java.gem ruby-debug-ide-0.4.6.gem activerecord-jdbcpostgresql-adapter-0.9.6-java.gem jdbc-postgres-8.3.604.gem activerecord-jdbcmysql-adapter-0.9.6-java.gem jdbc-mysql-5.0.4.gem activerecord-jdbc-adapter-0.9.6-java.gem rails-2.3.4.gem actionmailer-2.3.4.gem actionpack-2.3.4.gem activerecord-2.3.4.gem activeresource-2.3.4.gem activesupport-2.3.4.gem rack-1.0.0.gem rcov-0.8.1.5.0-java.gem
    [java] JAVA options: {:fork=>"true", :failonerror=>"true", :classname=>"org.jruby.Main", :maxmemory=>"512M"}
    [java] dist stage: dist/jruby-bin-1.5.0
    [java] JRuby limited openssl loaded. http://jruby.org/openssl
    [java] gem install jruby-openssl for full support.
    [java] Successfully installed columnize-0.3.1
    [java] Successfully installed rake-0.8.7
    [java] **************************************************
    [java]
    [java]   Thank you for installing rspec-1.3.0
    [java]
    [java]   Please be sure to read History.rdoc and Upgrade.rdoc
    [java]   for useful information about this release.
    [java]
    [java] **************************************************
    [java] Successfully installed rspec-1.3.0
    [java] Successfully installed ruby-debug-base-0.10.3.2-java
    [java] Successfully installed ruby-debug-ide-0.4.6
    [java] Successfully installed activerecord-jdbcpostgresql-adapter-0.9.6-java
    [java] Successfully installed jdbc-postgres-8.3.604
    [java] Successfully installed activerecord-jdbcmysql-adapter-0.9.6-java
    [java] Successfully installed jdbc-mysql-5.0.4
    [java] Successfully installed activerecord-jdbc-adapter-0.9.6-java
    [java] Successfully installed rails-2.3.4
    [java] Successfully installed actionmailer-2.3.4
    [java] Successfully installed actionpack-2.3.4
    [java] Successfully installed activerecord-2.3.4
    [java] Successfully installed activeresource-2.3.4
    [java] ERROR:  While executing gem ... (Errno::ENOENT)
    [java]     No such file or directory - c:\space\hudson\workspace\JMX-Tests\jdk\jdk1.6\label\WinXP-1-stable\o.jruby.distro\unpatched_source\jruby-1.5.0\dist\jruby-bin-1.5.0\lib\ruby\gems\1.8\gems\activesupport-2.3.4\lib\active_support\vendor\tzinfo-0.3.12\tzinfo\definitions\America\Argentina
    [java] rake aborted!
    [java] org.apache.tools.ant.ExitStatusException: Java returned: 1
    [java]
    [java] (See full trace by running task with --trace)
 [nbmerge] Failed to build target: all-o.jruby.distro 

The rake install_dist_gems task is run through Ant, it would need to be run the with --trace to get more details, but the Rake Ant task doesn't allow passing arguments to it. Will need to patch the task and add a property for turning on --trace on the hudsonqe machine. I think this is only happening on this one machine and isn't currently blocking anything (let me know if that's not the case so I know I should actively work on this).