fix(packaging)!: use --platform in pip instead of sitecustomize.py

Author: Creeper19472

src/serious_python/bin/package_command.dart

@@ -360,6 +360,8 @@ class PackageCommand extends Command {
               ...pipArgs,
               '--target',
               sitePackagesDir,
+              '--platform',
+              arch.value["tag"]!,
               ...requirements
             ], environment: pipEnv);
 

src/serious_python/bin/sitecustomize.dart

@@ -3,7 +3,7 @@ String sitecustomizePy = """
 # The folder containing this file should be on your PYTHONPATH pip is invoked.
 
 custom_system = "{platform}"
-custom_platform = "{tag}"
+# custom_platform = "{tag}"
 custom_mac_ver = "{mac_ver}"
 
 import collections