don't allow override

Author: silverwind

Makefile

@@ -100,9 +100,9 @@ GITHUB_REF_NAME ?= $(shell git rev-parse --abbrev-ref HEAD)
 # TODO: Remove this once we can raise the minimum Node.js version to 22.18 (alpine >= 3.23)
 NODE_VERSION := $(shell printf "%03d%03d%03d" $(shell node -v 2>/dev/null | cut -c2- | tr '.' ' '))
 ifeq ($(shell test "$(NODE_VERSION)" -lt "022018000"; echo $$?),0)
-	NODE_VARS ?= NODE_OPTIONS="--experimental-strip-types"
+	NODE_VARS := NODE_OPTIONS="--experimental-strip-types"
 else
-	NODE_VARS ?=
+	NODE_VARS :=
 endif
 
 ifneq ($(GITHUB_REF_TYPE),branch)