How can I make scala-maven-plugin recognize Cp1252 encoding?

I have several maven modules that use Cp1252 encoding. I had no problem with this coding until I added scala to one of the modules. The scala -maven plugin ignores the property project.build.sourceEncoding

and tries to parse the source files as if they were UTF-8.

I tried adding encoding to the plugin config:

<plugin>
    <groupId>net.alchim31.maven</groupId>
    <artifactId>scala-maven-plugin</artifactId>
    <version>3.1.6</version>
    <executions>
        <execution>
            <id>scala-compile-first</id>
            <phase>process-resources</phase>
            <goals>
                <goal>add-source</goal>
                <goal>compile</goal>
            </goals>
        </execution>
        <execution>
            <id>scala-test-compile</id>
            <phase>process-test-resources</phase>
            <goals>
                <goal>testCompile</goal>
            </goals>
        </execution>
    </executions>
    <configuration>
        <encoding>Cp1252</encoding>
    </configuration>
</plugin>

      

        
        
        
      

    

If that didn't work, I also tried adding the encoding to the execution:

<plugin>
    <groupId>net.alchim31.maven</groupId>
    <artifactId>scala-maven-plugin</artifactId>
    <version>3.1.6</version>
    <executions>
        <execution>
            <id>scala-compile-first</id>
            <phase>process-resources</phase>
            <goals>
                <goal>add-source</goal>
                <goal>compile</goal>
            </goals>
            <configuration>
                <sourceDir>${basedir}/scala</sourceDir>
                <encoding>Cp1252</encoding>
            </configuration>
        </execution>
        <execution>
            <id>scala-test-compile</id>
            <phase>process-test-resources</phase>
            <goals>
                <goal>testCompile</goal>
            </goals>
            <configuration>
                <sourceDir>${basedir}/scala</sourceDir>
                <encoding>Cp1252</encoding>
            </configuration>
        </execution>
    </executions>
    <configuration>
        <encoding>Cp1252</encoding>
    </configuration>
</plugin>

      

        
        
        
      

    

The module in question has 1,454 source files, so converting the module to use UTF-8 is impractical.