Meta: Extract platform detection utilities to their own file

This will be needed by other scripts.

To do so, this patch gives up on the importlib method of importing
packages. I tried extracting this helper to e.g. __init__.py, but the
python runtime was unable to find the imported symbols.

Meta/host_platform.py

@@ -0,0 +1,42 @@
+# Copyright (c) 2025, ayeteadoe <ayeteadoe@gmail.com>
+# Copyright (c) 2025, Tim Flynn <trflynn89@ladybird.org>
+#
+# SPDX-License-Identifier: BSD-2-Clause
+
+import enum
+import platform
+import sys
+
+
+class HostArchitecture(enum.IntEnum):
+    x86_64 = enum.auto()
+    AArch64 = enum.auto()
+
+
+class HostSystem(enum.IntEnum):
+    Linux = enum.auto()
+    macOS = enum.auto()
+    Windows = enum.auto()
+
+
+class Platform:
+    def __init__(self):
+        self.system = platform.system()
+        if self.system == "Windows":
+            self.host_system = HostSystem.Windows
+        elif self.system == "Darwin":
+            self.host_system = HostSystem.macOS
+        elif self.system == "Linux":
+            self.host_system = HostSystem.Linux
+        else:
+            print(f"Unsupported host system {self.system}", file=sys.stderr)
+            sys.exit(1)
+
+        self.architecture = platform.machine().lower()
+        if self.architecture in ("x86_64", "amd64"):
+            self.host_architecture = HostArchitecture.x86_64
+        elif self.architecture in ("aarch64", "arm64"):
+            self.host_architecture = HostArchitecture.AArch64
+        else:
+            print(f"Unsupported host architecture {self.architecture}", file=sys.stderr)
+            sys.exit(1)