Fix building layouts from JSON (#13310)

Broken by #12632.

build_layout.mk

@@ -7,7 +7,7 @@ define SEARCH_LAYOUTS_REPO
     LAYOUT_KEYMAP_C := $$(LAYOUT_KEYMAP_PATH)/keymap.c
     ifneq ("$$(wildcard $$(LAYOUT_KEYMAP_JSON))","")
         -include $$(LAYOUT_KEYMAP_PATH)/rules.mk
-        KEYMAP_C := $(KEYBOARD_OUTPUT)/src/keymap.c
+        KEYMAP_C := $(KEYMAP_OUTPUT)/keymap.c
         KEYMAP_JSON := $$(LAYOUT_KEYMAP_JSON)
         KEYMAP_PATH := $$(LAYOUT_KEYMAP_PATH)
     else ifneq ("$$(wildcard $$(LAYOUT_KEYMAP_C))","")
@@ -33,4 +33,5 @@ endif
 $(foreach LAYOUT,$(LAYOUTS),$(eval $(call SEARCH_LAYOUTS)))
 
 # Use rule from build_json.mk, but update prerequisite in case KEYMAP_JSON was updated
-$(KEYBOARD_OUTPUT)/src/keymap.c: $(KEYMAP_JSON)
+$(KEYMAP_C): $(KEYMAP_JSON)
+	$(QMK_BIN) json2c --quiet --output $(KEYMAP_C) $(KEYMAP_JSON)