Fix Windows detection in configure.ac - check both host_os and host

configure.ac

@@ -30,6 +30,12 @@ AM_CONDITIONAL([USE_OPENSSL], [test "x$with_openssl" = "xyes"])
 # Detect Windows for TUN implementation
 AC_MSG_CHECKING([for Windows])
 case $host_os in
+  *mingw* | *msys* | *cygwin* | *win*)
+    os_windows=yes
+    ;;
+  *)
+    # Also check $host for cross-compilation case
+    case $host in
       *mingw* | *msys* | *cygwin* | *win*)
         os_windows=yes
         ;;
@@ -37,6 +43,8 @@ case $host_os in
         os_windows=no
         ;;
     esac
+    ;;
+esac
 AC_MSG_RESULT([$os_windows])
 AM_CONDITIONAL([OS_WINDOWS], [test "x$os_windows" = "xyes"])