This is an attempt to fix command line limit problem reported in #3579. It's usual approach to work with a response file. So I adapted the code in question from passing the whole 25k command, that was truncated on 8191 character directly to ctx.action(), that was going through the shell:

ctx.action(
    inputs = inputs,
    outputs = [war],
    mnemonic = 'WAR',
    command = '\n'.join(cmd),
    use_default_shell_env = True,
)

with an intermediate step, generated shell script and pass it as executable to ctx.action() instead:

  # Executable script to generate war archive
  gen_war = ctx.new_file(ctx.label.name + "_gen_war.sh")
  ctx.file_action(gen_war, '\n'.join(cmd), True)

   ctx.action(
     inputs = inputs,
     outputs = [war],
     mnemonic = 'WAR',
     executable = gen_war,
     use_default_shell_env = True,
   )

This works as expected on Linux, but is failing on Windows with:

CreateProcess(): %1 is not a valid Win32 application.

I would expect that Bazel does some heuristic here and guess that the passed file is a shell script, for example, by trying to parse the first file line and see whether or not the first line is a shebang or something and shell out instead of trying to pass previously generated shell script directly to create process.