Don't unzip the sources which were bundled originally. Guix strips them from
the source and uses pre-build packages.

Taken from https://anonscm.debian.org/viewvc/pkg-java/trunk/libxerces2-java/debian/patches/02_build_dont_unzip.patch?revision=14507

Index: b/build.xml
===================================================================
--- a/build.xml
+++ b/build.xml
@@ -247,7 +247,7 @@
     <copy file="${src.dir}/org/apache/xerces/impl/xpath/regex/message.properties"
       tofile="${build.src}/org/apache/xerces/impl/xpath/regex/message_en.properties"/>
 
-    <!-- now deal with API's:  -->
+    <!-- not needed for Debian
     <unzip src="${src.apis.zip}" dest="${build.src}">
         <patternset
             includes="org/xml/sax/** 
@@ -270,6 +270,7 @@
                 org/w3c/dom/xpath/**"
         />
     </unzip>
+    -->
     
     <!-- substitute tokens as needed -->
     <replace file="${build.dir}/src/org/apache/xerces/impl/Version.java" 
@@ -1232,7 +1233,7 @@
     <replace file="${build.dir}/src/org/apache/xerces/parsers/AbstractSAXParser.java"
              token="return (fConfiguration instanceof XML11Configurable);" value="return false;"/>
  
-    <!-- now deal with API's:  -->
+    <!-- not needed for Debian
     <unzip src="${src.apis.zip}" dest="${build.src}">
         <patternset
             includes="org/xml/sax/** 
@@ -1255,7 +1256,7 @@
                 org/w3c/dom/xpath/**"
         />
     </unzip>
-
+    -->
 
     <!-- substitute tokens as needed -->
     <replace file="${build.dir}/src/org/apache/xerces/impl/Version.java" 
ut type='hidden' name='id' value='8b5339acfe381dca887b38634dcfdecae738ce7b'/><select name='qt'>
<option value='grep'>log msg</option>
<option value='author'>author</option>
<option value='committer'>committer</option>
<option value='range'>range</option>
</select>
<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=8b5339acfe381dca887b38634dcfdecae738ce7b'>root</a>/<a href='/guix/log/gnu?id=8b5339acfe381dca887b38634dcfdecae738ce7b'>gnu</a>/<a href='/guix/log/gnu/packages?id=8b5339acfe381dca887b38634dcfdecae738ce7b'>packages</a>/<a href='/guix/log/gnu/packages/bison.scm?id=8b5339acfe381dca887b38634dcfdecae738ce7b'>bison.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/packages/bison.scm?id=8b5339acfe381dca887b38634dcfdecae738ce7b&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2020-07-30 02:53:28 +0200'>2020-07-30</span></td><td><a href='/guix/commit/gnu/packages/bison.scm?id=8206a282b157fcf2d7435850587bf3ae29319698'>gnu: bison: Mention yacc in the description.</a><span class='msg-avail'>...</span></td><td>Jakub Kądziołka</td></tr>