Fix environmental variable check on Windows

.xonshrc

@@ -25,6 +25,9 @@ append_path("~/.local/bin")
 append_path("~/bin")
 append_path("~/go/bin")
 
+if in_win():
+	append_path("F:/programs/installed/micro")
+
 # tmux
 try:
 	requires("tmux")

functions.xsh

@@ -12,7 +12,8 @@ def in_wsl() -> bool:
 def in_win() -> bool:
 	"""Determines if the system is running inside a Windows environment."""
 
-	if ${'OS'} == "Windows_NT":
+	import os
+	if 'OS' in os.environ and os.environ['OS'] == "Windows_NT":
 		return True
 	return False