hadoop branch-0.20-append Build error:build.xml:933: exec returned: 1

[Alex Luya]

BUILD FAILED
......./branch-0 .20-append/build.xml:927: The following error
occurred while executing this line:
....../branch-0 .20-append/build.xml:933: exec returned: 1

Total time: 1 minute 17 seconds
+ RESULT=1
+ '[' 1 '!=' 0 ']'
+ echo 'Build Failed: 64-bit build not run'
Build Failed: 64-bit build not run
+ exit 1
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I checked content in file build.xml:
------------------------------------------------------------------------------------------------------------
line 927:<antcall target="cn-docs"/></target><target name="cn-docs"
depends="forrest.check, init" description="Generate forrest-based
Chinese documentation. To use, specify -Dforrest.home=&lt;base of Apache
Forrest installation&gt; on the command line." if="forrest.home">
line 933:<exec dir="${src.docs.cn}"
executable="${forrest.home}/bin/forrest" failonerror="true">
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It seems try to execute forrest,what is the problem here?I am running a
64bit ubuntu,with 64+32bit-jdk-1.6 and 64-bit-jdk-1.5  installed.Some
guys told there are some tricks in this
page:http://wiki.apache.org/hadoop/HowToRelease  to get forrest build to
work.But I can't find any tricks in the page.
Any help is appreciated.