Be sure to define defaults for NM,STRIP,OBJCOPY in Makefile.
diff --git a/Makefile b/Makefile
index da1f6a1..b294ed9 100644
--- a/Makefile
+++ b/Makefile
@@ -43,6 +43,10 @@
 Q=@
 endif
 
+OBJCOPY=objcopy
+NM=nm
+STRIP=strip
+
 .PHONY : all FORCE
 
 vpath %.c src