test: exit properly with swift_build_sdk_interface

`sys.exit` takes an integral value in the range of `0-127`.  Python 3 is
much more stringent about this and will convert the value if it is out
of the range to 1.  On Windows, explicitly use `ExitProcess` to ensure
that we get the correct value on the exit code which matters to `not`.

Author: compnerd

utils/swift_build_sdk_interfaces.py

@@ -416,6 +416,10 @@ def main():
     non_stdlib_module_files = (
         x for x in module_files if x.name != STDLIB_NAME)
     status = process_module_files(pool, non_stdlib_module_files)
+    if os.name == 'nt':
+        import ctypes
+        Kernel32 = ctypes.cdll.LoadLibrary("Kernel32.dll")
+        Kernel32.ExitProcess(ctypes.c_ulong(status))
     sys.exit(status)