Allow user overrides of LINKER_SCRIPT Make variable

Author: Max Vilimpoc

tools/export/makefile/Makefile.tmpl

@@ -58,9 +58,7 @@ LIBRARIES :={% for lib in libraries %} {{lib}} {% endfor %}
 
 # Allow user overrides of LINKER_SCRIPT from the command line, useful
 # if user wants to reserve specific flash areas for production config data
-ifndef $(LINKER_SCRIPT)
-LINKER_SCRIPT := {{linker_script}}
-endif
+LINKER_SCRIPT ?= {{linker_script}}
 {%- block additional_variables -%}{% endblock %}
 
 # Objects and Paths