bpo-44133: Link Python executable with object files (GH-30556)

When Python is built without --enable-shared, the "python" program is
now linked to object files, rather than being linked to the Python
library (libpython.a), to make sure that all symbols are exported.
Previously, the linker omitted some symbols like the Py_FrozenMain()
function.

When Python is configured with --without-static-libpython, the Python
static library (libpython.a) is no longer built.

* Check --without-static-libpython earlier in configure.ac
* Add LINK_PYTHON_OBJS and LINK_PYTHON_DEPS variables to Makefile.
* test_capi now ensures that the "Py_FrozenMain" symbol is exported.

Lib/test/test_capi.py

@@ -643,6 +643,24 @@ class CAPITest(unittest.TestCase):
         expected = compile(code, "<string>", "exec")
         self.assertEqual(result.co_consts, expected.co_consts)
 
+    def test_export_symbols(self):
+        # bpo-44133: Ensure that the "Py_FrozenMain" and
+        # "PyThread_get_thread_native_id" symbols are exported by the Python
+        # (directly by the binary, or via by the Python dynamic library).
+        ctypes = import_helper.import_module('ctypes')
+        names = ['PyThread_get_thread_native_id']
+
+        # Python/frozenmain.c fails to build on Windows when the symbols are
+        # missing:
+        # - PyWinFreeze_ExeInit
+        # - PyWinFreeze_ExeTerm
+        # - PyInitFrozenExtensions
+        if os.name != 'nt':
+            names.append('Py_FrozenMain')
+        for name in names:
+            with self.subTest(name=name):
+                self.assertTrue(hasattr(ctypes.pythonapi, name))
+
 
 class TestPendingCalls(unittest.TestCase):