Use Maven assembly plugin to set Linux file permissions even when run on other platforms?

This can be done using the fileMode parameter available in Maven Assembly Plugin assembly descriptor. For instance

<assembly>
    ...
    <fileSets>
        <fileSet>
            <directory>${project.build.directory}/bin</directory>
            <outputDirectory>/bin</outputDirectory>
            <includes>
                <include>*.sh</include>
            </includes>
            <fileMode>0755</fileMode>
        </fileSet>
        ...
    </fileSets>
    ...
</assembly>

It was asked in comments how to set permisions for directories, so that they don't end up with d--------- permissions. The answer is pretty straightforward - use directoryMode:

<assembly>
    ...
    <fileSets>
        <fileSet>
            <directory>${project.build.directory}/bin</directory>
            <outputDirectory>/bin</outputDirectory>
            <includes>
                <include>*.sh</include>
            </includes>
            <fileMode>0755</fileMode>
            <directoryMode>0755</directoryMode>
        </fileSet>
        ...
    </fileSets>
    ...
</assembly>