setup: Add support for macOS arm64/universal2 wheels. (#5583)

Now `python setup.py wheel_darwin_64bit` will generate a wheel whose
platform (architecture and macOS deployment target) matches those of
the bootloaders currently present in `PyInstaller/bootloader/Darwin-64bit`.

An unfortunate, but minor, side-effect of this change is that PyInstaller
itself must be installed to run `setup.py wheel_darwin_64bit`. As
this command isn't needed to install PyInstaller, we avoid any need
for bootstrap-installing.

PyInstaller/utils/osx.py

@@ -101,13 +101,35 @@ def get_macos_sdk_version(filename):
     header = binary.headers[0]
     # Find version command using helper
     version_cmd = _find_version_cmd(header)
+    return _hex_triplet(version_cmd[1].sdk)
+
+
+def _hex_triplet(version):
     # Parse SDK version number
-    major = (version_cmd[1].sdk & 0xFF0000) >> 16
-    minor = (version_cmd[1].sdk & 0xFF00) >> 8
-    revision = (version_cmd[1].sdk & 0xFF)
+    major = (version & 0xFF0000) >> 16
+    minor = (version & 0xFF00) >> 8
+    revision = (version & 0xFF)
     return major, minor, revision
 
 
+def macosx_version_min(filename: str) -> tuple:
+    """Get the -macosx-version-min used to compile a macOS binary.
+
+    For fat binaries, the minimum version is selected.
+
+    """
+    versions = []
+    for header in MachO(filename).headers:
+        cmd = _find_version_cmd(header)
+        if cmd[0].cmd == LC_VERSION_MIN_MACOSX:
+            versions.append(cmd[1].version)
+        else:
+            # macOS >= 10.14 uses LC_BUILD_VERSION instead.
+            versions.append(cmd[1].minos)
+
+    return min(map(_hex_triplet, versions))
+
+
 def set_macos_sdk_version(filename, major, minor, revision):
     """
     Overwrite the macOS SDK version declared in the given binary with

setup.py

@@ -147,11 +147,8 @@ def has_bootloaders(cls):
     # must check/update this tag.
     "Linux-64bit":  "manylinux2014_x86_64",
     "Linux-32bit": "manylinux2014_i686",
-    # The macOS version must be kept in sync with the -mmacosx-version-min in
-    # the waf build script.
-    # TODO: Once we start shipping universal2 bootloaders and PyPA have
-    #       decided what the wheel tag should be, we will need to set it here.
-    "Darwin-64bit": "macosx_10_13_x86_64",
+    # macOS needs special handling. This gets done dynamically later.
+    "Darwin-64bit": None,
 }
 
 # Create a subclass of Wheel() for each platform.
@@ -168,6 +165,49 @@ def has_bootloaders(cls):
     wheel_commands[command_name] = command
 
 
+class bdist_macos(wheel_commands["wheel_darwin_64bit"]):
+    def finalize_options(self):
+        """Choose a platform tag that reflects the platform of the bootloaders.
+
+        Namely:
+        * The minimum supported macOS version should mirror that of the
+          bootloaders.
+        * The architecture should similarly mirror the bootloader
+          architecture(s).
+
+        """
+        try:
+            from PyInstaller.utils.osx import get_binary_architectures,\
+                macosx_version_min
+        except ImportError:
+            raise SystemExit(
+                "Building wheels for macOS requires that PyInstaller and "
+                "macholib be installed. Please run:\n"
+                "    pip install -e . macholib")
+
+        bootloader = os.path.join(self.bootloaders_dir(), "run")
+        is_fat, architectures = get_binary_architectures(bootloader)
+
+        if is_fat and sorted(architectures) == ["arm64", "x86_64"]:
+            # An arm64 + x86_64 dual architecture binary gets the special name
+            # universal2.
+            architectures = "universal2"
+        else:
+            # It's unlikely that there will be other multi-architecture types
+            # but if one crops up, the syntax is to join them with underscores.
+            architectures = "_".join(architectures)
+
+        # Fetch the macOS deployment target the bootloaders are compiled with
+        # and set that in the tag too.
+        version = "_".join(map(str, macosx_version_min(bootloader)[:2]))
+
+        self.PLAT_NAME = f"macosx_{version}_{architectures}"
+        super().finalize_options()
+
+
+wheel_commands["wheel_darwin_64bit"] = bdist_macos
+
+
 class bdist_wheels(Command):
     """Build a wheel for every platform listed in the PLATFORMS dict which has
     bootloaders available in `PyInstaller/bootloaders/[platform-name]`.