env activate: use Win-compatible print on Windows (#42755)

Use "echo" instead of "printf" on Windows.

lib/spack/spack/cmd/env.py

@@ -270,7 +270,8 @@ def create_temp_env_directory():
 def _tty_info(msg):
     """tty.info like function that prints the equivalent printf statement for eval."""
     decorated = f'{colorize("@*b{==>}")} {msg}\n'
-    print(f"printf {shlex.quote(decorated)};")
+    executor = "echo" if sys.platform == "win32" else "printf"
+    print(f"{executor} {shlex.quote(decorated)};")
 
 
 def env_activate(args):