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"/>
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</td></tr></table>
<div class='path'>path: <a href='/guix/log/?id=a75387f8eeaacb242af66073c838485df1e87a10'>root</a>/<a href='/guix/log/gnu?id=a75387f8eeaacb242af66073c838485df1e87a10'>gnu</a>/<a href='/guix/log/gnu/build?id=a75387f8eeaacb242af66073c838485df1e87a10'>build</a>/<a href='/guix/log/gnu/build/bootloader.scm?id=a75387f8eeaacb242af66073c838485df1e87a10'>bootloader.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/build/bootloader.scm?id=a75387f8eeaacb242af66073c838485df1e87a10&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2022-06-24 10:21:06 +0200'>2022-06-24</span></td><td><a href='/guix/commit/gnu/build/bootloader.scm?id=62c86c8391ceb8953ca972498fd75ea9298b85ff'>image: Add support for 32bit UEFI.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/bootloader/grub.scm (grub-efi32-bootloader): New variable.
(install-grub-efi32): New variable.
* gnu/build/bootloader.scm (install-efi): Add a 'targets' keyword
argument.
(install-efi-loader): Likewise.
* gnu/build/image.scm (initialize-efi32-partition): New procedure.
* gnu/packages/bootloaders.scm (grub-efi32): New variable.
* gnu/system/image.scm (esp32-partition): New variable
(efi32-disk-image): New variable.
(efi32-raw-image-type): New variable.
(system-disk-image)[partition-image]: Set '#:grub-efi32' when
calling the partition initializer.

Signed-off-by: Mathieu Othacehe &lt;othacehe@gnu.org&gt;
</span></span></td><td>Denis 'GNUtoo' Carikli</td></tr>
<tr><td><span title='2021-11-12 13:26:52 +0000'>2021-11-12</span></td><td><a href='/guix/commit/gnu/build/bootloader.scm?id=fb3df2011692b2a6fea9f4fefd71dd788453fbae'>build: bootloader: Add GPT support.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/build/bootloader.scm (install-efi-loader): Add GPT support.
</span></span></td><td>Mathieu Othacehe</td></tr>
<tr><td><span title='2020-11-03 07:59:59 +0100'>2020-11-03</span></td><td><a href='/guix/commit/gnu/build/bootloader.scm?id=a38d861e571c952f78ca588b50bdcc4adcb0c88c'>system: reconfigure: Use the disk-installer if provided.</a><span class='msg-avail'>...<span class='msg-tooltip'>Fixes: &lt;https://issues.guix.gnu.org/44101&gt;.

* gnu/build/bootloader.scm (write-file-on-device): Pass 'no-fail flag instead
of 'no-create. Use a latin-1 transcoder.
* guix/scripts/system/reconfigure.scm (install-bootloader-program): Add a
"disk-installer" argument and use it as a fallback.
(install-bootloader): Adapt accordingly.
* gnu/tests/reconfigure.scm (run-install-bootloader-test): Ditto.
</span></span></td><td>Mathieu Othacehe</td></tr>
<tr><td><span title='2020-10-05 11:10:35 +0200'>2020-10-05</span></td><td><a href='/guix/commit/gnu/build/bootloader.scm?id=b97b423e3f61c80d5877dadc95b3f316cd61788f'>bootloader: Fix u-boot installation.</a><span class='msg-avail'>...<span class='msg-tooltip'>This is a follow-up of f19cf27c2b9ff92e2c0fd931ef7fde39c376adaa. The
bootloader installation must be done on the final disk-image, hence using
"disk-image-installer" instead of "installer" callback.

* gnu/bootloader/u-boot.scm: Turn all installer callbacks into
disk-image-installer callbacks.
* gnu/build/bootloader.scm (write-file-on-device): Open the output file with
'no-truncate and 'no-create options.
* gnu/system/image.scm (with-imported-modules*): Add (gnu build bootloader)
module.
</span></span></td><td>Mathieu Othacehe</td></tr>