Support Python 2.7 framework-style distributions on macOS 12

virtualenv's trick of adding a symlink to the base Python dylib
(`/Library/Frameworks/Python.framework/Versions/2.7/Python`) in the
virtualenv root, and rewriting the dependent dylib list of the
`<virtualenv>/bin/python` binary with the path of this symlink, no
longer works in macOS 12.

As of macOS 12, when <https://github.com/python/cpython/blob/v2.7.18/Modules/getpath.c>
computes `sys.prefix`, it ends up resolving the symlink. The result is
that `sys.prefix` points to the Python framework, e.g.
`/path/to/Python.framework/Versions/2.7` instead of at the virtualenv
root.

To mitigate this, add a _copy_ of the Python dylib into the virtualenv
instead of a symlink. To placate code signing (at least on Intel
machines), add a symlink to the `Resources` dir so the `Info.plist` file
is accessible.

Note that Apple's Python 2.7 distribution -- removed in macOS 12.3 but
previously located at /System/Library/Frameworks/Python.framework --
behaved differently to the python.org builds. It appears to have
incorporated custom patches to getpath.c to support virtualenv. See:
<https://github.com/apple-oss-distributions/python/blob/python-170.80.2/2.7/fix/getpath.c.ed>.

docs/changelog/2284.feature.rst

@@ -0,0 +1 @@
+Support for creating a virtual environment from a Python 2.7 framework on macOS 12 - by :user:`nickhutchinson`.

src/virtualenv/create/via_global_ref/builtin/cpython/mac_os.py

@@ -25,20 +25,11 @@ class CPythonmacOsFramework(CPython):
     def can_describe(cls, interpreter):
         return is_mac_os_framework(interpreter) and super(CPythonmacOsFramework, cls).can_describe(interpreter)
 
-    @classmethod
-    def sources(cls, interpreter):
-        for src in super(CPythonmacOsFramework, cls).sources(interpreter):
-            yield src
-        # add a symlink to the host python image
-        exe = cls.image_ref(interpreter)
-        ref = PathRefToDest(exe, dest=lambda self, _: self.dest / ".Python", must=RefMust.SYMLINK)
-        yield ref
-
     def create(self):
         super(CPythonmacOsFramework, self).create()
 
         # change the install_name of the copied python executables
-        target = "@executable_path/../.Python"
+        target = self.desired_mach_o_image_path()
         current = self.current_mach_o_image_path()
         for src in self._sources:
             if isinstance(src, ExePathRefToDest):
@@ -62,8 +53,8 @@ def _executables(cls, interpreter):
     def current_mach_o_image_path(self):
         raise NotImplementedError
 
-    @classmethod
-    def image_ref(cls, interpreter):
+    @abstractmethod
+    def desired_mach_o_image_path(self):
         raise NotImplementedError
 
 
@@ -74,13 +65,12 @@ def can_create(cls, interpreter):
             return super(CPython2macOsFramework, cls).can_create(interpreter)
         return False
 
-    @classmethod
-    def image_ref(cls, interpreter):
-        return Path(interpreter.prefix) / "Python"
-
     def current_mach_o_image_path(self):
         return os.path.join(self.interpreter.prefix, "Python")
 
+    def desired_mach_o_image_path(self):
+        return "@executable_path/../Python"
+
     @classmethod
     def sources(cls, interpreter):
         for src in super(CPython2macOsFramework, cls).sources(interpreter):
@@ -89,6 +79,14 @@ def sources(cls, interpreter):
         exec_marker_file, to_path, _ = cls.from_stdlib(cls.mappings(interpreter), "lib-dynload")
         yield PathRefToDest(exec_marker_file, dest=to_path)
 
+        # add a copy of the host python image
+        exe = Path(interpreter.prefix) / "Python"
+        yield PathRefToDest(exe, dest=lambda self, _: self.dest / "Python", must=RefMust.COPY)
+
+        # add a symlink to the Resources dir
+        resources = Path(interpreter.prefix) / "Resources"
+        yield PathRefToDest(resources, dest=lambda self, _: self.dest / "Resources")
+
     @property
     def reload_code(self):
         result = super(CPython2macOsFramework, self).reload_code
@@ -147,13 +145,21 @@ def fix_signature(self):
 
 
 class CPython3macOsFramework(CPythonmacOsFramework, CPython3, CPythonPosix):
-    @classmethod
-    def image_ref(cls, interpreter):
-        return Path(interpreter.prefix) / "Python3"
-
     def current_mach_o_image_path(self):
         return "@executable_path/../../../../Python3"
 
+    def desired_mach_o_image_path(self):
+        return "@executable_path/../.Python"
+
+    @classmethod
+    def sources(cls, interpreter):
+        for src in super(CPython3macOsFramework, cls).sources(interpreter):
+            yield src
+
+        # add a symlink to the host python image
+        exe = Path(interpreter.prefix) / "Python3"
+        yield PathRefToDest(exe, dest=lambda self, _: self.dest / ".Python", must=RefMust.SYMLINK)
+
     @property
     def reload_code(self):
         result = super(CPython3macOsFramework, self).reload_code