Adapted from Debian.
https://sources.debian.org/patches/jing-trang/20181222+dfsg2-6/unicode.patch/

Description: update unicode path
--- a/mod/regex/mod.xml
+++ b/mod/regex/mod.xml
@@ -46,7 +46,7 @@
 	    failonerror="yes">
 	<arg value="com.thaiopensource.datatype.xsd.regex.java.Categories"/>
 	<arg value="${build.dir}/mod/regex/gensrc/main"/>
-	<arg value="${lib.dir}/UnicodeData-3.1.0.txt"/>
+	<arg value="@GENTOO_PORTAGE_EPREFIX@/usr/share/unicode-data/UnicodeData.txt"/>
 	<classpath>
 	  <pathelement location="${build.dir}/mod/regex-gen/classes/main"/>
 	  <pathelement location="${build.dir}/mod/util/classes/main"/>