Add a test-sources configuration option. (#2062)

* Add test_sources configuration option.

* Add pyodide implementation.

* Modify default test behavior to run in the project directory.

* Update the test for running in the project directory.

* Apply suggestions from code review

Co-authored-by: Joe Rickerby <joerick@mac.com>

* Add shlex quoting to test-sources.

* Restructure ctypes example to avoid issues running from the project folder.

---------

Co-authored-by: Joe Rickerby <joerick@mac.com>

unit_test/options_test.py

@@ -24,6 +24,7 @@ skip = ["*musllinux*"]
 environment = {FOO="BAR"}
 
 test-command = "pyproject"
+test-sources = ["test", "other dir"]
 
 manylinux-x86_64-image = "manylinux1"
 
@@ -74,11 +75,13 @@ def test_options_1(tmp_path, monkeypatch):
     local = options.build_options("cp38-manylinux_x86_64")
     assert local.manylinux_images is not None
     assert local.test_command == "pyproject"
+    assert local.test_sources == ["test", "other dir"]
     assert local.manylinux_images["x86_64"] == pinned_x86_64_container_image["manylinux1"]
 
     local = options.build_options("cp37-manylinux_x86_64")
     assert local.manylinux_images is not None
     assert local.test_command == "pyproject-override"
+    assert local.test_sources == ["test", "other dir"]
     assert local.manylinux_images["x86_64"] == pinned_x86_64_container_image["manylinux2014"]