When the test source directory path contains symbolic links, that
directory might be placed earlier in the result of
`IRB::InputCompletor.retrieve_gem_and_system_load_path`, than other
directories in the source tree that are expanded to the real path. In
that case, the test file in "csv" under the test directory of csv gem
instead of the library path will be the first candidate, in
`TestIRB::TestCompletion#test_complete_require_library_name_first`.
```
<"'csv"> expected but was
<"'csv/helper">.
```
parallel test (`make test-all TESTS=-j8`) runs tests on specified
number of processes. However, some test checkers written in
`runner.rb` are not loaded. This fix enable these checkers on
parallel tests.
See also: https://github.com/ruby/ruby/pull/2508
As `make test-tool` does not use gems, and no Rubygems stuffs is
needed, so moved such things to test/runner.rb. Also no longer
nees `--test-target-dir` option.
tool/test/runner.rb had been copied from test/runner.rb.
test/runner.rb was for `make test-all`, and tool/test/runner.rb was for
`make test-testframework` and `make test-tool`.
But I want to avoid the code clones.
This change makes tool/test/runner.rb support --test-target-dir option
which allows tool/test/runner.rb to run `make test-all`.
Now we can remove test/runner.rb.
