Begin incorporating Python unit tests into build

We now build a separate APE binary for each test so they can run in
parallel. We've got 148 tests running fast and stable so far.

third_party/python/Python/progname.c

@@ -0,0 +1,27 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:4;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=4 sts=4 sw=4 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Python 3                                                                     │
+│ https://docs.python.org/3/license.html                                       │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "third_party/python/Include/pylifecycle.h"
+/* clang-format off */
+
+#ifdef MS_WINDOWS
+static wchar_t *progname = L"python";
+#else
+static wchar_t *progname = L"python3";
+#endif
+
+void
+Py_SetProgramName(wchar_t *pn)
+{
+    if (pn && *pn)
+        progname = pn;
+}
+
+wchar_t *
+Py_GetProgramName(void)
+{
+    return progname;
+}