fix: correct path when building sdist package (#1687)

* Edit path when building sdist package

This patch changes the working directory from the temp to the project
when building sdist package.This resolves issues with relative paths
in configuration files.

Resolves #1683

* Add a test for the `package` placeholder exposure

The change extends the existing test — `test_simple`. It checks that
the temporary wheel build directory is the project root extracted from
the source distribution. It does so by testing the presence of the
`setup.py` in the current working directory, as a side effect.

* Edit quotes in the CLI argument for Windows compatibility

Co-authored-by: Sviatoslav Sydorenko (Святослав Сидоренко) <wk.cvs.github@sydorenko.org.ua>

* Use single quotes to avoid syntax errors from f-string

Co-authored-by: Sviatoslav Sydorenko (Святослав Сидоренко) <wk.cvs.github@sydorenko.org.ua>

---------

Co-authored-by: Sviatoslav Sydorenko (Святослав Сидоренко) <wk.cvs.github@sydorenko.org.ua>

test/test_from_sdist.py

@@ -61,10 +61,23 @@ def test_simple(tmp_path):
     sdist_dir.mkdir()
     sdist_path = make_sdist(basic_project, sdist_dir)
 
+    setup_py_assertion_snippet = textwrap.dedent(
+        """
+        import os
+
+        assert os.path.exists('setup.py')
+        assert os.path.exists('{package}/setup.py')
+        """,
+    )
+    setup_py_assertion_cmd = f'python3 -c "{setup_py_assertion_snippet !s}"'
+
     # build the wheels from sdist
     actual_wheels = cibuildwheel_from_sdist_run(
         sdist_path,
-        add_env={"CIBW_BUILD": "cp39-*"},
+        add_env={
+            "CIBW_BEFORE_BUILD": setup_py_assertion_cmd,
+            "CIBW_BUILD": "cp39-*",
+        },
     )
 
     # check that the expected wheels are produced