Fix running tests in multi-project builds

[JonaLoeffler]

With the latest plugin version, running tests in my multi-project gradle build fails.

The project consists of a number gradle sub-projects like com.company.app.web.server.<component> for about 10 components. Each of these then has src/test/java.

cat: build/neotest-java/classpath.txt: No such file or directory
error: --class-path requires an argument
Usage: javac <options> <source files>
use --help for a list of possible options

The statusline briefly shows src/test/java is not accessible by the current user!, then Error reading file: /tmp/neotest-java/<some kind of id>/TEST-junit-jupiter.xml

This is my Lazy config for neotest:

return {
  {
    'rcasia/neotest-java',
    ft = 'java',
    dependencies = {
      'nvim-neotest/neotest',
      dependencies = {
        'nvim-neotest/nvim-nio',
        'nvim-lua/plenary.nvim',
        'antoinemadec/FixCursorHold.nvim',
        'nvim-treesitter/nvim-treesitter',
      },
    },
    config = function()
      require('neotest').setup {
        adapters = {
          require 'neotest-java' {
            ignore_wrapper = false, -- whether to ignore maven/gradle wrapper
          },
        },
      }

      vim.keymap.set('n', '<leader>tp', function()
        require('neotest').run.run(vim.uv.cwd())
      end, { desc = '[T]est [P]project', noremap = true })

      vim.keymap.set('n', '<leader>tf', function()
        require('neotest').run.run(vim.fn.expand '%')
      end, { desc = '[T]est [F]ile', noremap = true })

      vim.keymap.set('n', '<leader>tr', function()
        require('neotest').run.run()
      end, { desc = '[T]est [R]un', noremap = true })

      vim.keymap.set('n', '<leader>ts', function()
        require('neotest').run.stop()
      end, { desc = '[T]est [S]top', noremap = true })

      vim.keymap.set('n', '<leader>ta', function()
        require('neotest').run.attach()
      end, { desc = '[T]est [A]ttach', noremap = true })

      vim.keymap.set('n', '<leader>to', function()
        require('neotest').output.open()
      end, { desc = '[T]est output [O]pen', noremap = true })
    end,
  },
}

build/neotest-java/classpath.txt does exist in the working directory, but is empty.

Version v.1.10.0 still works as before.