This patch eliminates the need for providing "xjavac", which saves building a
package for the unmaintained "xerces-tools".

Taken from https://anonscm.debian.org/viewvc/pkg-java/trunk/libxerces2-java/debian/patches/01_xjavac_taskdef.patch?revision=14507

Index: b/build.xml
===================================================================
--- a/build.xml
+++ b/build.xml
@@ -39,7 +39,7 @@
   <property name="tools.dir" value="./tools"/>
 
   <!-- enable compilation under JDK 1.4 and above -->
-  <taskdef name="xjavac" classname="org.apache.xerces.util.XJavac">
+  <taskdef name="xjavac" classname="org.apache.tools.ant.taskdefs.Javac">
     <classpath>
       <pathelement location="${tools.dir}/bin/xjavac.jar"/>
     </classpath>
@@ -291,7 +291,7 @@
            source="${javac.source}"
            target="${javac.target}"
            classpath="${build.dir}/classes:${tools.dir}/${jar.apis}:${tools.dir}/${jar.resolver}:${tools.dir}/${jar.serializer}"
-           debug="${debug}"
+           debug="${debug}" nowarn="true"
            debuglevel="${debuglevel}"
            deprecation="${deprecation}"
            optimize="${optimize}"
@@ -359,7 +359,7 @@
            source="${javac.source}"
            target="${javac.target}"
            classpath="${build.dir}/classes:${tools.dir}/${jar.apis}"
-           debug="${debug}"
+           debug="${debug}" nowarn="true"
            debuglevel="${debuglevel}"
            includeAntRuntime="false"
            includeJavaRuntime="true"/>
@@ -379,7 +379,7 @@
            source="${javac.source}"
            target="${javac.target}"
            classpath="${tools.dir}/${jar.apis}:${build.dir}/classes:./tools/junit.jar"
-           debug="${debug}"
+           debug="${debug}" nowarn="true"
            debuglevel="${debuglevel}"
            includeAntRuntime="false"
            includeJavaRuntime="true"/>
e='search' size='10' name='q' value=''/>
<input type='submit' value='search'/>
</form>
</td></tr></table>
<div class='path'>path: <a href='/guix/log/?id=26169c80a682086e93bc607c81661b97faf3d903'>root</a>/<a href='/guix/log/etc?id=26169c80a682086e93bc607c81661b97faf3d903'>etc</a>/<a href='/guix/log/etc/teams?id=26169c80a682086e93bc607c81661b97faf3d903'>teams</a>/<a href='/guix/log/etc/teams/qt?id=26169c80a682086e93bc607c81661b97faf3d903'>qt</a>/<a href='/guix/log/etc/teams/qt/common.scm?id=26169c80a682086e93bc607c81661b97faf3d903'>common.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/etc/teams/qt/common.scm?id=26169c80a682086e93bc607c81661b97faf3d903&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2024-03-19 03:40:08 -0400'>2024-03-19</span></td><td><a href='/guix/commit/etc/teams/qt/common.scm?id=a8ba2f3507d03ec77506a03bf84d62f9cb439f8e'>teams: qt: Remove erroneous comment at top of scripts.</a><span class='msg-avail'>...<span class='msg-tooltip'>* etc/teams/qt/common.scm: Remove erroneous comment.
* etc/teams/qt/qt-manifest.scm: Likewise.
* etc/teams/qt/qt5-manifest.scm: Likewise.

Change-Id: I87a0ea669caa0ba5049b48a4f04fda58518c3f05
</span></span></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2023-08-22 12:32:20 -0400'>2023-08-22</span></td><td><a href='/guix/commit/etc/teams/qt/common.scm?id=0b994bb9b10b381376f1dfd8bd2bc9173ede2a66'>etc: Add Qt manifests for Qt maintenance.</a><span class='msg-avail'>...<span class='msg-tooltip'>* etc/teams/qt/common.scm: New file.
* etc/teams/qt/qt-manifest.scm: Likewise.
* etc/teams/qt/qt5-manifest.scm: Likewise.
</span></span></td><td>Maxim Cournoyer</td></tr>
b871ae8666d8f6de7440b.

With commit f743f2046be2c5a338ab871ae8666d8f6de7440b, responses to
pipelined GETs would end up being written concurrently by many threads.
Thus the body of those responses could be interleaved and garbled.

* guix/scripts/publish.scm: Revert
f743f2046be2c5a338ab871ae8666d8f6de7440b.
* tests/publish.scm ("/*.narinfo pipeline"): New test.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2022-02-14 11:23:56 +0100'>2022-02-14</span></td><td><a href='/guix/commit/tests/publish.scm?id=6adce1538d2df6fa2d68abc13ae94e2fa826d124'>publish: Do not sign the URL/Compression/FileSize narinfo fields.</a><span class='msg-avail'>...<span class='msg-tooltip'>This will allow mirror operators to alter these non-normative bits of a
narinfo without having to resign narinfos.

* guix/scripts/publish.scm (narinfo-string): Remove
URL/Compression/FileSize from BASE-INFO.  Move them after "Signature".
* tests/publish.scm ("/*.narinfo")
("/*.narinfo with properly encoded '+' sign")
("/*.narinfo with lzip + gzip")
("with cache, lzip + gzip"): Adjust accordingly.
* tests/substitute.scm ("query narinfo with signature over relevant subset"):
New test.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2022-01-19 22:07:54 +0100'>2022-01-19</span></td><td><a href='/guix/commit/tests/publish.scm?id=435ffae2f29ecaa94f3aca835d79e222bc1263d5'>tests: Adjust to gzip as the default log compression.</a><span class='msg-avail'>...<span class='msg-tooltip'>This is a followup to 575e52ac2b090fd194086e9c1c53bbf8055acbc2.

* tests/publish.scm ("/log/NAME"): Expect a gzip-encoded log.
</span></span></td><td>Ludovic Courtès</td></tr>