port 2P step 1: vendor CPython 2.7.18 as the mtpython static library

The embedded 40250 script layer needs its own interpreter on five platforms.
2.7 is end-of-life, so nothing can be fetched from the target SDKs and the
source is vendored (official 2.7.18 tarball, trimmed to 25MB; Lib/ stays for
step 3's python27.zip).

cpython-2.7.18/CMakeLists.txt builds one `mtpython` static library from exactly
the 133 objects the reference libpython2.7.a contains, off by default behind
-DMTGODOT_EMBED_PYTHON=ON. The source list and the built-in module table
(config/config.c, 39 entries) are shared; pyconfig.h is a probe result and is
not, so each platform keeps its own under config/<platform>/, regenerated by
tools/py_embed/gen_pyconfig.sh and checked against the shared table.

Three vendor patches, documented in docs/THIRD-PARTY.md: configure/configure.ac
learn arm64 on macOS, and posixmodule.c undefines the process-control calls it
hard-defines past pyconfig.h when building for iOS.

macOS (ctest python.embed: every builtin imports, codecs and pickle work off the
vendored Lib/), Android arm64 and iOS arm64 build. Linux needs a Linux host and
Windows needs a MinGW-vs-MSVC decision; both are noted for step 4.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

extension/third_party/cpython-2.7.18/Lib/distutils/errors.py

@@ -0,0 +1,88 @@
+"""distutils.errors
+
+Provides exceptions used by the Distutils modules.  Note that Distutils
+modules may raise standard exceptions; in particular, SystemExit is
+usually raised for errors that are obviously the end-user's fault
+(eg. bad command-line arguments).
+
+This module is safe to use in "from ... import *" mode; it only exports
+symbols whose names start with "Distutils" and end with "Error"."""
+
+__revision__ = "$Id$"
+
+class DistutilsError(Exception):
+    """The root of all Distutils evil."""
+
+class DistutilsModuleError(DistutilsError):
+    """Unable to load an expected module, or to find an expected class
+    within some module (in particular, command modules and classes)."""
+
+class DistutilsClassError(DistutilsError):
+    """Some command class (or possibly distribution class, if anyone
+    feels a need to subclass Distribution) is found not to be holding
+    up its end of the bargain, ie. implementing some part of the
+    "command "interface."""
+
+class DistutilsGetoptError(DistutilsError):
+    """The option table provided to 'fancy_getopt()' is bogus."""
+
+class DistutilsArgError(DistutilsError):
+    """Raised by fancy_getopt in response to getopt.error -- ie. an
+    error in the command line usage."""
+
+class DistutilsFileError(DistutilsError):
+    """Any problems in the filesystem: expected file not found, etc.
+    Typically this is for problems that we detect before IOError or
+    OSError could be raised."""
+
+class DistutilsOptionError(DistutilsError):
+    """Syntactic/semantic errors in command options, such as use of
+    mutually conflicting options, or inconsistent options,
+    badly-spelled values, etc.  No distinction is made between option
+    values originating in the setup script, the command line, config
+    files, or what-have-you -- but if we *know* something originated in
+    the setup script, we'll raise DistutilsSetupError instead."""
+
+class DistutilsSetupError(DistutilsError):
+    """For errors that can be definitely blamed on the setup script,
+    such as invalid keyword arguments to 'setup()'."""
+
+class DistutilsPlatformError(DistutilsError):
+    """We don't know how to do something on the current platform (but
+    we do know how to do it on some platform) -- eg. trying to compile
+    C files on a platform not supported by a CCompiler subclass."""
+
+class DistutilsExecError(DistutilsError):
+    """Any problems executing an external program (such as the C
+    compiler, when compiling C files)."""
+
+class DistutilsInternalError(DistutilsError):
+    """Internal inconsistencies or impossibilities (obviously, this
+    should never be seen if the code is working!)."""
+
+class DistutilsTemplateError(DistutilsError):
+    """Syntax error in a file list template."""
+
+class DistutilsByteCompileError(DistutilsError):
+    """Byte compile error."""
+
+# Exception classes used by the CCompiler implementation classes
+class CCompilerError(Exception):
+    """Some compile/link operation failed."""
+
+class PreprocessError(CCompilerError):
+    """Failure to preprocess one or more C/C++ files."""
+
+class CompileError(CCompilerError):
+    """Failure to compile one or more C/C++ source files."""
+
+class LibError(CCompilerError):
+    """Failure to create a static library from one or more C/C++ object
+    files."""
+
+class LinkError(CCompilerError):
+    """Failure to link one or more C/C++ object files into an executable
+    or shared library file."""
+
+class UnknownFileError(CCompilerError):
+    """Attempt to process an unknown file type."""