Add platform-specific arch option unit test

cibuildwheel/util.py

@@ -124,13 +124,16 @@ class DependencyConstraints:
 
 
 class Architecture(str, Enum):
+    # mac/linux archs
     x86_64 = 'x86_64'
     i686 = 'i686'
     aarch64 = 'aarch64'
     ppc64le = 'ppc64le'
     s390x = 's390x'
-    win32 = 'win32'
-    win_amd64 = 'win_amd64'
+
+    # windows archs
+    x86 = 'x86'
+    amd64 = 'AMD64'
 
     @staticmethod
     def parse_config(config: str, platform: str) -> 'List[Architecture]':

unit_test/main_tests/main_platform_test.py

@@ -93,3 +93,21 @@ def test_archs_argument(platform, intercepted_build_args, monkeypatch, use_env_v
     build_options = intercepted_build_args.args[0]
 
     assert build_options.architectures == [Architecture.ppc64le]
+
+
+def test_archs_platform_specific(platform, intercepted_build_args, monkeypatch):
+    monkeypatch.setattr(platform_module, 'machine', lambda: 'x86_64')
+    monkeypatch.setenv('CIBW_ARCHS', 'unused')
+    monkeypatch.setenv('CIBW_ARCHS_LINUX', 'ppc64le')
+    monkeypatch.setenv('CIBW_ARCHS_WINDOWS', 'x86')
+    monkeypatch.setenv('CIBW_ARCHS_MACOS', 'x86_64')
+
+    main()
+    build_options = intercepted_build_args.args[0]
+
+    if platform == 'linux':
+        assert build_options.architectures == [Architecture.ppc64le]
+    elif platform == 'windows':
+        assert build_options.architectures == [Architecture.x86]
+    elif platform == 'macos':
+        assert build_options.architectures == [Architecture.x86_64]