Merge pull request swiftlang#20787 from compnerd/windows-target

test: define the target architecture for Windows

Author: compnerd

test/lit.cfg

@@ -338,6 +338,10 @@ swift_version = lit_config.params.get('swift-version',
 lit_config.note('Compiling with -swift-version ' + swift_version)
 config.swift_test_options = '-swift-version ' + swift_version
 
+if run_os == 'windows-msvc':
+  if run_cpu == 'x86_64':
+    config.swift_test_options += ' -Xcc -D_AMD64_'
+
 test_options = os.environ.get('SWIFT_TEST_OPTIONS')
 if test_options:
     config.swift_test_options += ' '