Change VPATH path addition order (#5754)

Specifically, to fix some edge cases, and keep the handling consistent, the userspace folder should not actually be added at the end.  Ideally, it should be added after the keymap paths, but before the keyboard's path.

This issue was discovered in #5484, and the fix created by mtei.

build_keyboard.mk

@@ -334,9 +334,9 @@ SRC += $(KEYBOARD_SRC) \
 
 # Search Path
 VPATH += $(KEYMAP_PATH)
+VPATH += $(USER_PATH)
 VPATH += $(KEYBOARD_PATHS)
 VPATH += $(COMMON_VPATH)
-VPATH += $(USER_PATH)
 
 include common_features.mk
 include $(TMK_PATH)/protocol.mk