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"/>
lect>
<input class='txt' type='search' size='10' name='q' value=''/>
<input type='submit' value='search'/>
</form>
</td></tr></table>
<div class='path'>path: <a href='/guix/log/?id=9466afbac6c9d51c6cd9a0f947d2a92f0bea0024'>root</a>/<a href='/guix/log/gnu?id=9466afbac6c9d51c6cd9a0f947d2a92f0bea0024'>gnu</a>/<a href='/guix/log/gnu/installer?id=9466afbac6c9d51c6cd9a0f947d2a92f0bea0024'>installer</a>/<a href='/guix/log/gnu/installer/newt?id=9466afbac6c9d51c6cd9a0f947d2a92f0bea0024'>newt</a>/<a href='/guix/log/gnu/installer/newt/page.scm?id=9466afbac6c9d51c6cd9a0f947d2a92f0bea0024'>page.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/gnu/installer/newt/page.scm?id=9466afbac6c9d51c6cd9a0f947d2a92f0bea0024&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2024-11-11 07:28:34 +0100'>2024-11-11</span></td><td><a href='/guix/commit/gnu/installer/newt/page.scm?id=e57bc3bcde9fc200c9196e94b29bf7b5b427411e'>installer: Fix file-name typos.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/installer/newt/page.scm (run-dump-page): Typo file-name.
* gnu/installer/utils.scm (open-new-log-port): Likewise.

Change-Id: I837991a0ee5054b3afa8328205e23ac6f9fbae8d
</span></span></td><td>Janneke Nieuwenhuizen</td></tr>
<tr><td><span title='2022-11-15 12:16:43 +0100'>2022-11-15</span></td><td><a href='/guix/commit/gnu/installer/newt/page.scm?id=6b39c3afccbc2fa91746f379f46f6acfa47c8f62'>installer: Error page width is parameterized.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/installer/newt/page.scm (run-error-page): Add #:width and honor
it.
</span></span></td><td>Ludovic Courtès</td></tr>