diff --git a/build/core/definitions.mk b/build/core/definitions.mk
new file mode 100644
index 0000000..c2c157c
--- /dev/null
+++ b/build/core/definitions.mk
@@ -0,0 +1,6 @@
+#
+# CM-specific macros
+#
+define uniq
+$(if $1,$(firstword $1) $(call uniq,$(filter-out $(firstword $1),$1)))
+endef