Mixed Java/Kotlin IDEA project - Ant build not working

I have created a mixed Java/Kotlin project in IDEA 2019.3.1 under OpenJDK 13.0.1. I generated a single-file ant build. Build > Build Project works fine within IDEA, whether using the bundled Ant (1.10.5) or my installed version (1.10.7). However, I would like to be able to build the project using my installed Ant from the command line, or possibly other IDEs. However, even after cleaning, attempting to build using Build > buildfilename fails, as does attempting to build from the command line. Errors like the following occur at spots in the Java code that reference Kotlin code:

[javac] C:\ProjectPath\src\com\somemodulepath\SomeJavaClass.java:16: error: cannot find symbol
[javac] import static com.somemodulepath.SomeKotlinFileKt.methodName;
[javac]                                  ^
[javac]   symbol:   class SomeKotlinFileKt
[javac]   location: package com.somemodulepath
[javac] C:\ProjectPath\src\com\somemodulepath\SomeJavaClass.java:16: error: static import only from classes and interfaces
[javac] import static com.somemodulepath.SomeKotlinFileKt.methodName;
[javac] ^

I have not added anything in Build File Properties under any of Properties, Execution > Ant command line, or Additional Classpath. I tried changing the settings in Build > Generate Ant Build; they had no effect.

Based on the info at https://kotlinlang.org/docs/tutorials/command-line.html, I tried adding the following lines in the appropriate places of the generated build.xml file:

<typedef resource="org/jetbrains/kotlin/ant/antlib.xml" classpath="${path.variable.kotlin_bundled}/lib/kotlin-ant.jar" />
...
<withKotlin/>

Doing so resulted in the error:

<withKotlin> task does not yet support the fork mode

Can anyone provide a good way to create a working Ant build for a mixed Java/Kotlin IDEA project? Thanks!