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=3ad93a94586d28a37b4e4cd60210fa5ba2040ed7'>root</a>/<a href='/guix/log/gnu?id=3ad93a94586d28a37b4e4cd60210fa5ba2040ed7'>gnu</a>/<a href='/guix/log/gnu/system?id=3ad93a94586d28a37b4e4cd60210fa5ba2040ed7'>system</a>/<a href='/guix/log/gnu/system/accounts.scm?id=3ad93a94586d28a37b4e4cd60210fa5ba2040ed7'>accounts.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/system/accounts.scm?id=3ad93a94586d28a37b4e4cd60210fa5ba2040ed7&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2023-10-05 23:14:54 +0200'>2023-10-05</span></td><td><a href='/guix/commit/gnu/system/accounts.scm?id=97927608cb4f9c5d721115f1cb638de17ac38e62'>Revert "system: accounts: Export &lt;user-account&gt;."</a><span class='msg-avail'>...<span class='msg-tooltip'>This reverts commit 03795e2ba27424fc98957da00f6c71325e7ae425.
Fixes &lt;https://issues.guix.gnu.org/66279&gt;.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2023-08-20 02:00:00 +0200'>2023-08-20</span></td><td><a href='/guix/commit/gnu/system/accounts.scm?id=5a2c3352d8f8a08a5ba01542a3f282799e503d33'>Revert "gnu: system: Add home-directory-permissions field to &lt;user-account&gt;."</a><span class='msg-avail'>...<span class='msg-tooltip'>This reverts commit e9a5eebc785cb843034b38c5c5a6dd10904bdf2a, which
as far as I can tell breaks system roll-backs thusly:

[...]
In gnu/build/accounts.scm:
   239:27  3 (_ #&lt;&lt;password-entry&gt; name: "root" password: "x" uid: 0 gid: 0 real-name: "System &gt;)
In unknown file:
           2 (string-join ("root" "x" "0" "0" "System administrator" "/root" #t) ":" #&lt;undefined&gt;)
In ice-9/boot-9.scm:
  1685:16  1 (raise-exception _ #:continuable? _)
  1685:16  0 (raise-exception _ #:continuable? _)

ice-9/boot-9.scm:1685:16: In procedure raise-exception:
In procedure string-append: Wrong type (expecting string): #t
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2023-08-25 15:12:54 +0200'>2023-08-25</span></td><td><a href='/guix/commit/gnu/system/accounts.scm?id=e9a5eebc785cb843034b38c5c5a6dd10904bdf2a'>gnu: system: Add home-directory-permissions field to &lt;user-account&gt;.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/system/accounts.scm (&lt;user-account&gt;)[home-directory-permissions]: New
field.
(user-account-home-directory-permissions): New accessor.
* gnu/build/activation.scm (activate-users+groups): Use home directory
permission bits from the user account object.
* doc/guix.texi (User Accounts): Document new field.

Signed-off-by: Josselin Poiret &lt;dev@jpoiret.xyz&gt;
</span></span></td><td>David Thompson</td></tr>
<tr><td><span title='2023-07-26 10:40:16 -0400'>2023-07-26</span></td><td><a href='/guix/commit/gnu/system/accounts.scm?id=03795e2ba27424fc98957da00f6c71325e7ae425'>system: accounts: Export &lt;user-account&gt;.</a></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2019-03-25 23:37:06 +0100'>2019-03-25</span></td><td><a href='/guix/commit/gnu/system/accounts.scm?id=cf848cc0a17a3a58d600116896f6e7abfb0440d4'>accounts: Add default value for the 'home-directory' field of &lt;user-account&gt;.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/system/accounts.scm (&lt;user-account&gt;)[home-directory]: Mark as
thunked and add a default value.
(default-home-directory): New procedure.
* doc/guix.texi (User Accounts): Remove 'home-directory' from example.
* gnu/system/examples/bare-bones.tmpl: Likewise.
* gnu/system/examples/beaglebone-black.tmpl: Likewise.
* gnu/system/examples/desktop.tmpl: Likewise.
* gnu/system/examples/docker-image.tmpl: Likewise.
* gnu/system/examples/lightweight-desktop.tmpl: Likewise.
* gnu/system/install.scm (installation-os): Likewise.
* gnu/tests.scm (%simple-os): Likewise.
* gnu/tests/install.scm (%minimal-os, %minimal-os-on-vda):
(%separate-home-os, %encrypted-root-os, %btrfs-root-os): Likewise.
* tests/accounts.scm ("allocate-passwd")
("allocate-passwd with previous state"): Likewise.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2019-03-07 20:05:09 +0100'>2019-03-07</span></td><td><a href='/guix/commit/gnu/system/accounts.scm?id=6061d01512081c93c53fdd1d4302b36696403061'>activation: Operate on &lt;user-account&gt; and &lt;user-group&gt; records.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/system/accounts.scm (sexp-&gt;user-group, sexp-&gt;user-account): New
procedures.
* gnu/system/shadow.scm (account-activation): Call them in the arguments
to 'activate-users+groups'.
(account-shepherd-service): Likewise.
* gnu/build/activation.scm (activate-users+groups): Expect a list of
&lt;user-account&gt; and a list of &lt;user-group&gt;.  Replace uses of 'match' on
tuples with calls to record accessors.
(activate-user-home): Likewise.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2019-03-07 20:04:02 +0100'>2019-03-07</span></td><td><a href='/guix/commit/gnu/system/accounts.scm?id=f6f67b87c08fe7b901db834c714aceaef2b62b60'>system: Add (gnu system accounts).</a><span class='msg-avail'>...<span class='msg-tooltip'>The (gnu system accounts) module is meant to be used both on the build-
and on the host-side.

* gnu/system/shadow.scm &lt;top level&gt;: Call 'default-shell'.
(&lt;user-account&gt;, &lt;user-group&gt;): Move to...
* gnu/system/accounts.scm: ... here.  New file.
* gnu/local.mk (GNU_SYSTEM_MODULES): Add system/accounts.scm.
</span></span></td><td>Ludovic Courtès</td></tr>